Kerrits size L black performance riding tights

Kerrits black size L riding tights with inner drawstring. Alright. So my kid sat in something whilst wearing these tights, and the butt area has some ??? on it. It is not sticky, but it feels slightly hardened. I’m not even gonna try to get it out 🤷‍♀️ The knee patch area is in excellent condition. The Kerrits label on the hip came off. No holes, rips, tears, etc. Bundle and save! I have tons of outgrown riding gear in size M and L kids.