Yes, I belive that this is Ensolite, the classic insulating lining material for molded fiberglass trailers. Most of the 17' Bolers seem to have a less dense soft plastic yellow foam with a thin very flexible suface layer, but the earlier/smaller Bolers and early Scamps have the dense black Ensolite with a durable surface layer. I'm suprised this is in a 1988 model, since someone at Scamp
told me that they switched to aluminized plastic bubble insulation (currently Reflectix) covered by fabric ("ratfur") in 1987.
Ensolite is normally used in quite thin sheets - about 3/8" seems to be common, but its not easy to measure foam, and the stuff in my Boler
is very soft and probably never was the same thickness as the black version. Benny K. has both 13' and 17' Bolers, and thus an interior in each kind of foam - he confirmed that they are different types.
Ensolite is still a current brand name, no longer with Uniroyal, but it's hard to find.
For small detached areas not at a seam (like a bubble), many owners report success reattaching it with glue using a syringe to inject it through the foam. For larger areas, spray cement is the usual preference. 3M Hi-Strength 90 was recommended to one owner by 3M customer service, and that's also what I chose just reading the labels in the store. It has noxious fumes, so lots of ventilation is required, and only a single coat is required to hold the lighter foam in my Boler
1700 quite securely. 3M's Spray 70 adhesive might work well, and is apparently less noxious.
Covering the seams is a whole technical speciality of its own, normally involving some sort of tape (the original Boler
method) or trim (apparently used in other brands). I have no idea what was done in Scamps.