The are three distinct backup systems. The autosave timer and the
.blend2 files are part of separate systems.
From my answer here:
There are several backup systems in Blender:
Temporary files (saved every 2 minutes by default)
These will be saved in your temporary directory (specified in User
preferences > File) with a random number as the name.
You can quickly open an auto saved file by pressing File > Recover
auto save, then selecting the auto saved file (the modification times
can be very useful for determining which file to pick):
You can adjust the interval at which these are saved in
CtrlAltU User preferences > File >
Auto save > Timer:
Temporary quit files (saved on quit)
These are also saved in your temporary directory, with the name
quit.blend. You can quickly open it by pressing File > Recover
Persistent save files for reverting accidental/unwanted saves (saved when saving)
These are saved as
.blend2, etc. files in the same
directory as the current .blend. .blend1 will be the file as it was
the save before your last save, .blend2 will be the save before the
save before your last save, etc.
To open these files, navigate to the directory where your file was
saved and enable backup files in the display filter:
You can configure the number of these to save in User preferences >
Without knowing more about your particular situation (how long it's
been, has tmp been cleared, how often did you save, etc.), it's hard
to say which will work best. There's no risk to trying them all, beware that
\Temp is normally cleared out at some point,
so get any useful backups out while you can.
On most Linux systems,
/tmp is either stored in RAM or cleared on startup, so files will not survive a crash/reboot.
To avoid this, you can set your autosave directory to someplace besides
/tmp. See this question for details.
Temp files are not deleted by default, so your backups should be floating around in there somewhere.