I believe section 8.C.2 Deadhead Deviation Banks, applies:
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 plus the value of any scheduled deadheads for recurrent training. However, if a deadhead trip is changed or canceled by the company, the deadhead bank monies remain intact. A deadhead associated with a carryover trip shall be credited to the deviation bank for the bid period containing the showtime for the deadhead.
Intent: If the pilot does not fly a deadhead trip the deviation bank will be reduced accordingly ,e.g., drop without pay, bump by another line pilot, trip trade, etc.

It looks like unless the trip is taken away by scheds, i.e., not dropped because of substitution refusal, that you may lose the bank money. However, did they offer to bump the other trip? If not, you may have an a arguement. So, our pal David should be your next call. Let us know the answer and the outcome.