I'm pretty sure that's what happened. Party City had a whole sign apologizing for the switch to nitrogen about the same time we were having trouble getting dewa

I'm pretty sure that's what happened. Party City had a whole sign apologizing for the switch to nitrogen about the same time we were having trouble getting dewars to refill our scanner and I talked to the owner about it so I don't think it was confusing the floating balloons with the other balloons. But you're right it makes little sense in terms of buoyancy and that hadn't occurred to me at the time. Maybe it was actually a switch to a helium/nitrogen blend. I can also see replacing helium completely for those balloons that get tied into shapes (animals etc), but that's a tiny sliver of the balloon market I'd assume.