Here's something I've always noticed. Early on in the movie, Mentalino believes that Harry and Lloyd are professionals that had been watching them for weeks. He even says as much, pointing out how they knew about his "gas" problem. So later in the movie, without wearing a disguise or anything, he pretends to be a hitchhiker so they would pick him up. If he thought they had been watching him and his partner for weeks, wouldn't they know who he is when they pick him up? Is this a plot hole?
Oh ok, well in that case he would have hitchhiked in the hopes of getting the briefcase back with or without his gun. Since he was planning on using rat poison at the restaurant he could have been side planning to mention who he was in the previous belief but it backfired no thanks to his ulcer.
Dude, are you one of the characters in this movie? You still don't get it.... he's saying that if Harry & Lloyd were the kind of people that Mental thought they were, the hitchhiking plan never would have worked. So it made no sense for him to use it.
Good catch, OP. I was thinking the same thing when I saw it