Phuck that! First, you are on the right track with your thinking. Laundry drainage is famous for bringing pumps to a halt, and it's typically long strings from clothing, wrapping the impellor, that bring the pump to a stop. Those long dangly pieces that wear off the bottoms of jeans are the biggest culprit.
I would unplug the pump and dig into it. If it's hard plumbed into the pump reservoir, don't worry, just neatly cut the pipes a few inches above the container. Take it apart and see it the impellor is jammed. It may be as simple as disassembling the impellor housing and carefully cutting all the debris off. Take a good look at the float mechanism and be sure that it's operating freely also. If you decide to test it, take it outside, plug it in, and flood the intake with a hose. Stand back since it will pump a pretty impressive plume straight up, unit the float drops and turns it off. There should be a check valve in the system that prevents the reservoir from being filled by water draining back down the discharge pipe, make sure that it is functioning also. If you need a new pump, there will be enough info on the old one to find a replacement online. The final step for reassembly is to buy a pair of "Fernco" couplings at Home Depot. These are repair couplings that are essentially pieces of rubber hose with clamps that can be slipped over the cuts you made, to reconnect the pipes. While you are at HD, find a hose sock filter that fits the discharge hose from the washer. This will filter the discharge and prevent this from happening again. Good luck, it's actually a pretty easy job. PM me if you run into trouble.
