Good question. My opinion: his record. Sinclair has an admittedly tainted past with prior arrests, drug issues, etc. all of which he openly acknowledged. My guess is he's alive bc they could play the "you can't trust this nutjob with a criminal record" card.

But otherwise, you're right. Like the Kiltons, BO's circle has a tendency to master "convenient suicide suddenly" anyone with dirt.

It's also possible BO forgot about this fling entirely (??). Sounds like he probably had too many to count.