Sure, I get that, and with a couple doses given I agree that not having ANY change would be odd. It just seems that the first thing to consider in this case would be the simplest and easiest correctable solution, which would be that, for whatever reason, the sux isn't working, and to try something new. As the OP described it the pt was allready apneic, so you can't even gauge if there'd been an effect by looking at their respiratory rate/pattern.
I don't know if there's more info out there, but the abstract I linked to, while only showing pretty small decreases in strength after 4-6 weeks at 25C did mention that at 40C the rate was higher. I don't know how the OP's department works, but it's far from unheard of for rigs parked in an apparatus bay to get damned hot during the summer months. Hitting 100F might be pushing it, but over 75F would be pretty routine until the engine was turned on. For people keeping sux uncooled until the manufacturers expiration (as it appears the OP does) something to think about.
And I'm still very curious if/when the ER doc pushed his own paralytic, and what it was.