Welcome to thermal flying 101. Thermals are desirable in sailplane flying, but they can be hazardous, as you've found out.

Live and learn, but you probably exacerbated the situation by keeping the plane in a tight circle. It probably stayed smack dab in the middle of the thermal. Flying straight might've allowed the plane to come out of the thermal.

Anyway, it's GREAT to hear that you're having a blast, and that these little setbacks aren't discouraging you Don't you wonder where these planes were when you were a kid? Heck, even 7 years ago?