Also, sometimes maya will save an extra file, in the same directory as the original but its not always obvious unless you select 'all files' in the drop down file type menu.

It does occasionally save an invisible mb file but will look something like this example:

'my model name'.mb xf12hfhakfjflslslswxef

so its worth looking for that at well. the file will be bigger too but if you do have one reopen it and just save as something else.

Jay