We had this happen once with Alamo (by DLR, actually). We dropped off after hours... even saw the car in the Alamo lot as we walked by the next morning to DLR, boxed in by other cars at that point... Got a call around noon asking us where we were. Luckily it did get resolved but we kind of got the run around on the phone with them periodically throughout the day, either they'd say they hadn't found it or whoever answered the phone couldn't answer us. We had to keep calling them to follow up, they didn't call us. We stopped in the next morning before going to DLR and asked at the counter and they were just like oh yeah, it was there, no issues. Gee thanks. At least they figured it out because it was gone by then, they must have rented it again
Hopefully this gets squared away for you. Where are you at? I'd keep checking in with them periodically if they are not good about calling you for an update...