Where did it come from?

For 12 days I was in Delhi and when I came back, I noticed a huge grey lizard (call it paapi) with spots on its back, in fact, the biggest one seen thus far almost the size of Hulk's palm, roaming inside my kitchen. It spooked me terribly and made my legs rubbery and left me wondering about its point of entry. I was so confident about the newly sealed kitchen window! Even though R tried to find paapi, it hid somewhere.
But then, the next day evening, I found paapi trying to navigate through the wire mesh covering the window. It was struggling hard that I could hear the sound of paapi banging itself of the wire mesh. Then i realised maybe it entered past the three frames and then the kitchen and then could not find its way out. Paapi panicked and hopped into the sink and I had to pester my mother to kill it and flush it down the toilet. Then I sealed the two sliding panes so that they would not enter inside by any chance, which has made the kitchen like a preheated oven.
I would rather cook myself than have a huge gecko around my kitchen. The fear for lizards will never subside as long as I live! So bring it on Geckos - I am your TERMINATOR!!! DO NOT MESS WITH ME!