PDF file not created and vanishes from Folder

I am new to LaTeX and have about 20 pages completed on a recent project I’m working on. When I run the .tex file I have saved, I get the error "failed to find file ‘…pdf’; perhaps it has been deleted" and I can’t view the file.

Luckily I saved the PDF, but it was many pages ago. I can put the PDF back in the folder where the location is, and I can then view it within LaTeX, but as soon as I run the script, it goes away (as in it is not in the folder I just put it in, as well as is not in the TeX viewer).

Any advice?