I had about 10 tabs of open, saved documents, and was closing them all out to move on to something else. I held Command+W down, and accidentally held it down past when all of the tabs were closed. Textastic crashed, and, when I tried to reopen it, OS X's "Verifying..." window came up briefly, indicating that the application's signature had changed somehow. I have Gatekeeper disabled, but I still had to re-install Textastic from the App Store to get it to open again.
Customer support service by UserEcho