Going back to the beginning, this is what I think we know based on the articles, press releases and interviews previously linked in the thread. Apologies if I've muddled or missed any details. Take it as IMO:
Dave was running late from a previous load and called his wife, Sarah, asking her to set out a change of clothes for him. When Dave arrived home between 7:00-7:30pm (sources differ on the exact time) he told Sarah he needed pants with deeper pockets, and either he or Sarah went upstairs to get a different pair. Dave gave Sarah and his grandson Niko a kiss as he was leaving, but told his 10-year-old son Joseph there wasn't enough time to give him a hug or kiss. Sarah remembers that Dave was wearing Wrangler pants and cowboy boots. She can't remember the colour of his shirt, and to my knowledge hasn't mentioned the colour of the pants or boots.
Dave arrived for the pick-up at Eagle Grove later than expected and was the last to load. The site has been searched and there's no publicly-released evidence of anything suspicious or unusual happening at the loading site. He left the loading site at 10:50pm.
Dave's trip from Eagle Grove to Marker 126 seems to have followed the expected timeline. He arrived at 11:15pm and stopped for 16 minutes. He was seen on camera checking the truck and his phone. There's no confirmation on whether he made a phone call. Other truckers have said this was likely a normal check on the truck prior to delivering a load. Nothing suspicious was seen on the video and there was no sign of a third party. Sarah looked at a video still and confirmed the man in the video is Dave, but she refused to watch the whole video because she didn't want it to be her last memory of him. Dave's truck was subsequently caught on a DOT camera heading west along Hwy 20 towards his destination.
Dave reached the Hwy 20/71 intersection within the expected timeframe at 12:18am. There's no evidence from cameras or paperwork that Dave ever reached his destination at Wiechman's, nor that he met with any third parties on the road--that doesn't mean he didn't meet anyone, but there's no publicly-released evidence that he did.
For whatever reason, Dave's truck turned north along Union Avenue instead of south along Hwy 71. The truck traveled four miles in the wrong direction before being parked on a quiet section of N14/Union Avenue close to the D15/190th St intersection. Data shows the truck traveling north to its final location, which it reached by 12:40am. There's no proof that Dave was driving, but equally, no evidence anyone else was. Driving from the 20/71 intersection to the N14/D15 intersection shouldn't take 22 minutes, but it's unclear if the truck was moving slowly, or remained stationary for extended periods of time along the way.
The parked truck was passed by a male friend who works feeding pigs, first at 5:30am and again on his return at 7:30am. The friend didn't think it was suspicious and assumed Dave was dealing with whatever the problem was.
Sarah was visited by Dave's boss later that morning, who informed her Dave never delivered his load. The boss and Dave's other colleagues spent the next few hours searching Dave's most likely route(s). Sarah called Dave's phone a number of times, without response. At 2:23pm Sarah reported Dave missing to the Lake View Sheriff's Office. She reported it as a medical issue because she had been told LE would respond more quickly--this may or may not have affected LE's initial handling of the case. At 3:04pm a Sac County road employee reported the truck to the Sac County Sheriff's Office.
A female officer called Sarah using Dave's phone, which was still inside the truck along with his wallet. Nothing was missing from the wallet, including $2000 in cash. Dave's old orange jacket was found in a ditch nearby, along with a pocketknife, phone charger and towel. Early reports of a muck boot and gloves being found may be incorrect. A tracker dog followed Dave's scent to a nearby field entrance, but reports differ on whether the dog lost the scent, or was called off due to poor weather conditions.
Thermal imaging cameras, drones, and ground searches were conducted for the next two days. Nothing was found. The weather was very cold with snow falling a few days after Dave went missing. It's unclear how wide the radius of the initial search was. Jake Rowley and the United Cajun Navy later conducted wide-ranging searches using drones, ATVs, horses and ground volunteers. They searched approximately 100,000 acres along Dave's presumed route. They also found nothing connected to Dave.
LE have examined many possiblities, including the possibility of Dave taking a flight or otherwise leaving the country. They have found no evidence he crossed any borders.
Dave's wife, Sarah, and his friends and colleagues don't believe he would leave by choice, nor that he would leave a load of pigs unattended. However, Sarah has admitted Dave has high blood pressure and would often tell her, "I can't take this." He has a loan for a new truck requiring $2000 per month repayments. Sarah quickly opened fundraising accounts after Dave went missing and admitted they relied on his paycheck.
Whatever happened, it happened when Sarah's daughter (Dave's stepdaughter) and grandson were visiting. Over the summer Dave had taken his twin sons, Joseph and Isaack, out with him on the truck for the first time. Dave grew up in Sac City and is familiar with the area.
Dave has had previous run-ins with LE and may have had previous addiction issues, but there's no public evidence of current problems, nor of any other drug-related issues.
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I've tried to keep my personal opinions out of this and just lay out the known details.