What did they do?
They discovered a stash of Tramadol, which appears to be the drug of choice for Gaza smugglers.
According to these officials, the Mossad smuggles Tramadol into Gaza via organized crime rings. The Mossad works together with Sinai Bedouin to bring the drugs into Gaza via smuggling tunnels.
I would compliment them on their imagination, but when every story ends with "The Israelis did it!," it gets a little boring after a while.