Chances are the cleaners will have found the iPad rather than the cabin crew, and I somehow doubt their honesty, particularly in Turkey where the value of the iPad is probably similar to their monthly wage.
It's always easy to blame 'cleaners' and often unfairly so. There was a spate of thefts of personal items at a company I contracted for in France. The cleaners were, of course, blamed. Investigation proved that the culprit was a well paid locally employed (i.e. French) member of the company's permanent staff.
When I was backpacking in Turkey, many years ago, I was often told that if anything was stolen it was more likely that the thief was a tourist than a local. I found the Turks unfailingly honest, trusting, and hospitable. Things may have changed, but I would trust them before many other nationalities.