It so happened that Shreyas was shooting for the Making of Paying Guest, in which he had to shoot his co-stars' interviews.
So after he finished Celina Jaitley's interview and had to interview the next one, he realized his cell phone was missing. He looked for the phone all over the sets and was getting paranoid about losing it, when lightning struck and he called used one of his colleagues' cell and called his phone.
He found it hidden in an obscure corner and it was after he found it that he came to know that it was Celina who hid the phone. And guess what, everyone else knew about the prankster side of Celina.
Guess Shreyas will have to be a little more careful about his cell phone now and of course think twice before playing a prank on Celina.