Take it with you on an international trip or three. Surely those airport scanners will pick it up.
Besides, if I was in a terrorist cell, had a pager for communicating, and was taking a vacation flight, I think I might leave that pager behind for a week.
They weren't flagged because they went into Lebanon which has very little import security, and because it was a supply chain attack.
The batteries were swapped for a combination battery / explosive charge. The follow-up attack where Hezbollah moved to using walkie-talkies that were also rigged to explode was the real shocker, though.
No