Your page isn't lost but just the working file as you have force quit Wappler. You can just reopen the last saved file and it should be ok.
We are however improving the process so in the next update even on crash or force quit - your work will always be saved (even if you haven't saved)
But back to your original problem about the Google Maps marker, so each time you place a marker the Wappler freezes? Could you post this is a bug and include the Wappler log files as described in: