Recovery of the score in musescore

1. "I accidentally deleted it, and I can't recover it, when I try to open it it says it can't find it"
Where do you save your scores? On your own computer, or "in the cloud"?

2 "... when I try to open it it says it can't find it and reports saying that I'm not connected to musescore"
This suggests that your "Recent files" list is pointing to the cloud. You can log in to musescore.com with your usual MuseScore ID and look for the option "My scores".

That will allow you to check whether your score still exists as a score file (.mscz format).

3. "Could they get me back the project?"
You still have the PDF file. So... using MuseScore you can do this yourself, with the menu option File > Import PDF.... It took me only a couple of minutes to upload your PDF with this option, and to get the downloaded MuseScore file (.mscz) created by the optical music recognition (OMR).

The recovered score is attached. You will need to tidy up the .mscz score by redefining the instruments, but I think the notation is mainly correct.