No, you don't keep the bank money. The CBA says in Chap.8.C.2.a:
Deadhead Deviation Banks
a. A pilot shall have a deviation bank established for each bid period. The value of the deviation bank shall equal the value of the scheduled deadhead tickets for trips flown during the bid period.
You actually have to fly the trip in order to keep the bank money. No fly = No money. Sorry.