I created a project and ran it successfully many times. Unfortunately, Construct2 then crashed, and now the project no longer exists. Does Construct save things when you run them?
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I'm afraid no.
Construct2 saves project when you save them only.
Construct 2 crashing should not delete anything off your computer! Did it crash when you clicked save or at another time? Construct 2 doesn't access the files of your project until you click save so it's hard to imagine how crashing at a different time could have deleted anything.