If you have access to fold3, you will find details here about Leppla's loss:
https://www.fold3.com/image/268402014
Liska flew as a gunner with VS-10 on 26 October 1942, the day Leppla was shot down, and claimed a Zero.
https://www.fold3.com/image/268401776?terms=Liska
Liska then survived another battle with Zeroes on 14 November 1942, two pairs of SBD fighting several Zeroes and one US plane being shot down while Liska's escaped.
https://www.fold3.com/image/267969669 (and next page)
After this date, a search of fold3 returns no entry for John Liska (I searched Liska actually, and there is a Frank Liska KIFA with VB-117 on 6 June 1944)
He survived his last known battle and is not in the available US Navy casualty list (that is still a work in progress according to authors):
http://www.naval-history.net/WW2USca...USNbyNameL.htm
But that proves nothing: the Frank Liska listed above is not on the above list either.