This is a real shot in the dark, but if you're owt like me then no doubt you've found locks, pumps, lights, etc in the road at some point.
I managed to lose the sensor from my white Knog Nerd Computer in North Wales on Monday. I cannae be sure but think I remember reading the display on my way back into Conwy ... but on leaving Conwy after food/coffee I realised the sensor had dropped off.
My guess is that it is somewhere between Bangor and Conwy (likely Conwy) ... if by some divine miracle you should come across it, let me know and we'll arrange postage costs, etc for it to be returned.
Otherwise I may just have to bite the bullet and finally buy a Garmin/Bryton - an expense I can well dow ithout at present.