"He's fucking someone else. Nobody needs to go missing overnight, and certainly not for two nights. There is literally no other reason for this" and "C'mon, what grown, adult man chooses to doss down for the night on a friend's uncomfortable sofa or even more uncomfortable floor, when he has a nice comfy bed at home to go to?"
Because he's off his head on coke - Jesus!!
Do you know how people behave on cocaine or what it does to them? It often causes the bowels to open so they go for a shit, they don't care about how clean or unclean they are, they don't care where they end up or in what state - because they a off their tits on cocaine!
I'm not ruling out there being another woman but in my 'D'XBF's case, his coke binges involved no one but himself and the drugs - because people who use these drugs are inherently self centred.
These may be a series of 'one-offs' (which they clearly aren't, however sporadic, there is clearly a pattern) - is OP feeling repercussions from them right now? Yes she is. Does it raise questions about her partner and their relationship that will last long after today? Yes.
Please, do not underestimate the very significant effect such 'one-offs' have or just HOW significant the drug aspect is.