This is kiin lao, I’ve picked up from here before (and maybe they changed) but they’ve never done driver self pick-up. You normally have to get the order from someone at the counter. Looks like OP said that it wasn’t even the right restaurant, my guess is the driver was assigned multiple orders and messed up and gave him the other customers order.

I have had it happen. When speaking to owners at our favorite place they have had drivers argue over orders and swap right on front of them.
After the owners specifically pointed which was which.

In our experiences over the last year, service has gone downhill. I have used them for a longtime over multiple cities. Something is off in parts of the Pgh area.