Yes, $5K for a Scamp 13 of that era with a bathroom was cheap. Someone likely pounced on it.
If you are looking for a deal, you have to be ready to launch, as your competition (other buyers) will be ready too.
The first thing I would look at on a Scamp is the floor. Crawl UNDER the trailer and look up at the floor. Then test above for soft spots. Floor rot can be fixed, but read some threads on that topic to decide if you want to go through that process.
Typically I would not expect to see a Scamp 13 with a bathroom at that price, unless it was a big project. I would have guessed more like $8K or more in very good condition. Check out the sold listings on the
fiberglass for sale web site to get a feel for value.
Molded FG trailers priced under market sell super fast. We priced our Casita below market just to move it. Sold in less than 4 hours, and I live in the middle of nowhere.
Finding a used 13 footer with a bathroom will be challenging. Sorry you missed this one.