While using Standard Maple, a backup file: *.bak is created automatically in the same folder as the original .mw file and Maple by default automatically saves your file at standard intervals (default equals 3 minutes, see Tools Menu, Options, General Tab to reset this parameter).
If Maple crashes for any reason, you can rename the current copy so it is safe, and then change the backup extension back to .mw to then open the last autosaved version. of your file. However, if you reopen Maple first and then reopen the last saved copy of the file (last meaning the last copy you deliberately saved), it will delete the autosaved backup which may be much more recent. Check dates (times) and sizes. Be forewarned.
For some of you, the Maple Student Help Center might prove useful. It offers on-line help: "Get real answers from real people" "within hours" for homework problems by posting your questions on the on-line Forum. Free registration at Maple Primes is required for access.