"I do agree that Missy, as a victim was random, but I do not believe that particular church was random at all." -- In some way, that has to be true, because Loser Perp didn't just walk down the street and saunter into this church. He did pick to be there. The problem we have is in knowing why they picked this particular church and at this specific night, and we probably have to first know who did it and why to answer that question of why they picked it. Was it the location, some perceived ease of access or egress or of being undiscovered, some connection to the church, some info LP knew that made him think this was an easy or good place to get into, was it MB that drew him there, was it somehow originally picked at random, or some other reason we just don't consider? We can't objectively eliminate any of those, other than just using our own "bias" to decide on an answer and work from there, sad to say.
"I’m sure the police/investigators ... checked for camera footage from businesses, homes & traffic cameras in a widening circle around the church to see if the car was caught on camera at another location in which the license plate and/or driver was more visible because they were less careful thinking that they were away from the scene." --- Yes they did. The challenge is that even if someone caught the perp's car on camera, the limits of technology make it virtually impossible to make out the license of a car going 60 mph or so, and it was raining, and the road is a good ways from any camera. Even in the video of the car at SWFA across the street that night, going 5-10 mph, up close, and stopping at times, the license was illegible. LE tried, however, every place up and down that highway for quite a ways. Unfortunately, with such a highway, perp could easily have been 30 or more miles away before stopping, and before the murder was discovered, as there is quick access to multiple interstate-style highways (including US 287, US 67, I-35, I-20, and I-45) in less time than that.
"Did the investigation keep the church closed to the public for a while...?" --- Nope, LE was only there for a day or two, during which time they gathered whatever evidence they needed, and then the church was back in full service.
"I have wondered if something outside the box like this was used to kill Missy." --- Nope, it was a handgun that killed her. Plain and simple. There is no mystery to unravel. LE saw the body up close, saw the wounds, there was a full autopsy, and LE went looking for ammo sales in prior days hoping to get lucky on perp buying the ammo (which should make it clear what they knew). The FBI records (they were there from the outset to aid the investigation, as was ATF and other LE groups) recorded the murder's "Weapon" as "Handgun - pistol, revolver, etc". The murderdata.org site obtained their info from the FBI's public files. I have personally seen the FBI files too, multiple times (but not a user-friendly setup or search engine, it took many hours each time of pure trial-and-error to get there, so I finally decided never again), which is accessible if you have the patience to wade through their setup.
LE literally refused to comment on how she was killed, saying they would talk about that later, then never doing so, even to this day. That speaks volumes. In two early SWs they speak of vaguely of tools, and an unknown instrument (of death), with one also mentioning puncture wounds, but never actually say directly how she was killed, and imo they were trying to mislead the curious without actually lying, to keep under wraps that she was shot. Technically, a gun is a tool for shooting people, and a bullet wound punctures the skin. The discovery of the FBI records let the cat out of the bag, but LE still isn't asked about it afaik, and I suspect they would decline to answer if asked.
"The search warrant would've specifically indicated a gun, casings, etc, rather than "unknown instrument" as the murder weapon if she died from a gunshot" --- Obviously not true, since the FBI records the murder weapon was indeed a handgun.
But in relation to this SW's wording, LE (imo) hastily covered more than they really needed to, and so in order to keep facts behind their curtain, it appears they fuzzied some detail as they did so. This was their 1st SW, asking for permission to search MB's vehicle she arrived in (because she was found murdered) for anything that might give them a clue as to what happened and why. How she was murdered didn't matter at all (for purposes of getting a SW to look in her car), and it's enlightening that all the warrants obtained after that one and one other (those 2 were in the 1st 36 hours) basically said NOTHING about the death other than it was a murder being investigated and describing the perp as seen in the video. You can even look at the SW's and see how the first couple were slapped together hastily, with part of them hand-written, with mark-throughs, and sloppy wording. But I think they got some training as they went, because after that the SW's were professional, with polished content, formal affidavits attached (which removed any need to say much about the murder itself, and only in repeated, precise, finely crafted wording), and so on.
One note to keep in mind about all the various SWs - they are each written in a way that recites "facts" that may actually be nothing more than guesses, or possibilities being explored, but offering them up in a way that makes them sound concrete and that justifies the search being requested at that time. The next SW might say just the opposite, chasing a different suspect or angle. The ones in this case contain a graveyard of ideas and since-disproven theories of the crime. Reader beware.