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?
I'm afraid no.
Construct2 saves project when you save them only.
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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.