Borosilicate glass for monoprice delta mini gets warped


Hello. Yesterday i got my new cutted sized borosilicate glass from amazon for my monoprice mini delta. And i attached it to the bed and i usually heat the bed 60 degrees for pla and after few prints one of them really long one i cleaned the glass and as i felt it with my hands. It felt no longer flatted anymore with a really small mountains across the glass. I really need an explanation. Isnt borosilicate glass supposed to handle the heat well without warping? And if not then what is the uniqueness of it and what better in comparision to standard glass. Any advice what to do in this situation? Any related good ideas you can give. Thanks a lot