Suspected of *****ing sweets

I walked out of the store with my baby carrying a pack of sweets that I had bought in the store. As I walk out the surety at the doors asks me where I bought the sweets from and I said in the store then I walked out. He follows me outside demanding a receipt for the sweets and demanding to search me. So I refused saying he can't make those demands as I am out of the store even if I was inside I find it stupid in this day and age that any security would do that. Anyway, this guys drags me from escalator to demand me to go back to the store so he can do his search