Has my IC been fried by the reversed battery
Most likely, yes, because as you said:
it was working before the motor disconnected and my dad put the battery in backwards
In general, ICs are very sensitive to reverse polarity of their power connections. Replace the LM393 and re-test.
If you didn't already use an IC socket to hold the IC, then remove the existing IC, solder an IC socket in its place, then insert the replacement IC (the correct way round) in that socket.
If there is an ongoing possibility of someone reversing the battery connections (depending on your battery type and how much force is applied to the battery connector!) then you could consider adding a suitable diode in series with the power input. Then, if the battery is connected again with reverse polarity, no significant current would flow and no components would be damaged.
Using a Schottky diode would have a slightly lower forward voltage drop than a typical silicon rectifier diode. Your choice depends on what is available to you and what voltage drop across the diode your design can accept (I expect that this is not critical on your design).
The chosen diode also needs to be rated to cope with whatever maximum current (IF(AV)) your design can draw from the battery (plus some margin) e.g. with the motors stalled. This means that, for example, a 1N4148 won't be suitable as its IF(AV) rating can be around only 150mA (depending on the diode manufacturer) and your motors might draw more than that, especially when stalled (you should check).
The chosen diode must also have a suitable voltage rating (VDC). However for a 9V power supply, it would be difficult to find a power diode rated less than that, so this is unlikely to be a limiting parameter.