There are lots of sketchy things about this case.
1 - Jena saw Branson rush into the kitchen and take something out one of the cabinets, then run out the back door. When he returned, she asked what's happening, he didn't tell anything and he acted like nothing happened.
2 - Jena then took a shower and after she came out from the bathroom she saw one of the men that were working on the car going through the cabinets in the kitchen as well. She asked him what he was looking for and he told her nothing and went back outside.
3 - The last time Jena saw Branson, she asked where he was going and and he told her he was going to put the jumper cables in the storage shed and would be right back. This was the last time Branson was seen. She never saw him again. The men that had been working on the car claim to have never seen him. No one saw him.
4 - A few days before his disappearance, on April 7, Branson visited his neighbor, Jason Biermann, and he was inadvertently drugged. While intoxicated, he allegedly danced around the house nude, shaved his pubic hair, and then engaged in sex with Biermann. After the incident, Branson confessed it to his father and was upset as he felt he had been taken advantage of. Perry's father, Bob, said he knew that his son was homosexual and suspected he had had encounters with men in the past, and was angry with Biermann for "drugging and then using his son."
5 - In 2024, authorities revealed that drugs could've been a factor in this case. Authorities got tips that after leaving his home that day, Perry was sighted at a house a mile east of Quitman, Missouri, a house known at the time as a popular place to buy drugs particularly. However, the house was destroyed by fire less than a week after Branson's disappearance.
These are my opinions based on the info I gave above:
1 - The mechanics knew that Branson was hiding something and Branson was aware of it. So Branson acted quick and ran into the kitchen, checked the cabinets and found what he was looking for, quickly got rid of it or hid it somewhere else where they couldn't find it. This explains why the mechanic left and went back outside without saying anything after Jena asked what he was looking for, because he couldn't find it and didn't want to cause a scene. As for what was Branson hiding, it could be anything, money, drugs, etc..
2 - I'm not sure if the neighbor was interrogated (I could be wrong) but I do think that he was somehow involved in Branson's disappearance. The fact that he drugged Branson when he went to visit him shows that he somehow had access to getting drugs. I think it's possible that Branson went to this neighbor to get some drugs, something happened between them and they started arguing at things went wrong.
3 - Jena probably did not tell everything, I'm thinking that maybe she skipped some details in order to not to get in trouble. She might have seen something that she wasn't supposed to see and could have gotten threatened. But I find it really weird how she left after her friend never showed up again after claiming that he would be right back. I also find it weird that she took a shower there. Personally I wouldn't take a shower at my friend's house even if I feel so dirty, I'd go to my house for it. Maybe she took a shower to get rid of some evidence?