What would make the compression drop on engine and not start?

Tow it out of this shop, it sounds like they are stringing you along without doing any work. Not touching a car for two weeks is ridiculous. As to the engine, check timing and check for a possible dropped valve. There's no way of knowing what abuse an engine took, such abuse isn't going to show up on a Carfax. I suspect the previous owner knew it and unloaded car before engine blew up. If you have no legal recourse (research your state's Lemon Laws) then you'll have to decide whether to fix engine or replace it or sell it as is and let someone else deal with it.

Thank you, One other thing, the mechanic who replaced valve cover said he took on test drive and red lined it to make sure would hold up. Is that normal?

Redlined the engine? Stupid but not harmful for an engine in good shape but I wonder if the engine slipped time. Lemon laws don't apply to used cars.