Kick


I find it easier when that circumstance happens to freeze the track then clone the resulting wave to another track then unfreeze track and mute or archive the midi and its audio counterpart if your happy with the result.  Sometimes bouncing wasn't working even though I could hear the output it would record it with almost no volume or none (what's the differnce LOL).  Other times it did work which seemed purely random, very frustrating.  Hence I got happy with the workaround.  Other way would be as mentiond to export audio (main outputs) with just the drums playing and than import it back.
 
When bouncing a synth, you have to choose the output with the highest signal, preferably one you can control.
If the output of the synth track is high enough (-6 to 0 dB) and you select Tracks as the output from which to bounce, the bounced track should be at the same level. Same for buses. If the synth track is output to a bus and the bus level is good and high, not clipping, choosing Buses as the source, the bounced level would be the same.