You are very correct. You will never find a MKIV "shell" in a junkyard. Turbo Toys in Tampa rebuilds alot of salvage title MKIV that he resells for $20K and up, but they will have a salvage title forever. They last MKIV I saw that had no motor and had minor accident damage, they were asking $10k for I believe.
If you really want a MKIV project and can't afford a TT look for a high milage NA automatic. They can be had for around $10-$12K if you find an old lady that has had one forever. There are a few around.