Sold A Car 11 Months Ago And Just Received Notice That It Was Impounded And I'm Responsible For The Fees. What Can I Do?

Hi, so I sold my old college car for $300 back in January 2024 on OfferUp. The car is registered in Florida, but sold in Washington state. I never sold a car before, but tried to follow the steps I found online: transferred the paper title over and filled out a bill of sale. However, I never submitted the bill of sale to the DOL, just thought I needed it for my records.

Fast forward to today, my mom sends me a pic of a letter she got from the WA department of licensing saying that my old car has been impounded for two weeks and I'm responsible for the fees incurred or else the car will be auctioned off. I call the number provided that leads to the impound company that says I can either pay to get my car back which is $2,100 as of today or wait for the car to be auctioned off and whatever proceeds are made will be deducted from that balance ($500 potential sale deducted for $2,100+ fees), but I would still need to pay the leftover balance or else it will go to collections.

As expected, I was very much in shock when I learned all of this. I thought after I sold the car, this would all have been out of my hands. However, I do know that I am responsible since I never submitted the bill of sale. However, I'm confused as to how the buyer of my car had been driving it around for the past 11 months without it registered in his name?

All this to say, I'm not too sure what I can do. I do not want the car back so I do not want to pay the $2,100 to get it back, but I also don't want to wait for the auction and build up more fees the longer the car is in storage. The impound company did offer a settlement of $800 to just wipe my hands clean of the car and they take it to auction without me getting any proceeds. So my question is, what should I do here? Do I take the settlement or do I have any rights that can rid me of the fees? Thank you.