Three possibilities spring to mind -
1) This was left where it was to prove a point, and the person responsible is looking forward to watching his creation unfold on the news/media, with a satisfied smirk on his/her face
or
2) Somebody genuinely wanted to transport this device from A to B, but got cold feet at the other end, not wanting to risk a pat down after disembarking.
or
3) They wished to use it for not so innocent purposes, but again, lost their bottle mid-flight and stuffed the thing in the first available place that wasn't on their person or in their hand luggage.
Air marshal, anyone?
