Eric, if I am correct you are now testing your system relying on the fact that a previously good air bag when re installed will be leak free.
There is however the possibility that in the removal, and re install process that something happened to that bag and it will leak. Of course you have already gone through the process, so you might as well follow through. If the bus stays put you succeeded.

I think a better way to test the original air bag in a speedier fashion (less time waiting for parts, and less remove and replace), could have been the instalation of a cap on the end of the line feeding the suspect airbag, thus isolating it from the system and proving that anything beyond the cap is at fault for whatever reason.