OOPS?

The question is. . . . WHY/HOW?

It's too big for a mouse & too tiny for a rat = young Rat.

Question:-
Has it been in the shed & found the Warfarin? Doubt it, there was little enough left after the wee moosies; which I have seen, rat never.
Has my crop of unrequested, unidentified fungi seen it off? We'll never know.
Did it find a neighbour's Warfarin? NO idea & not asking.
If it was too tiny to get out from inside; how the great grey green greasy Limpopo did it get in over the much higher side?
I think I'll just inter it & let nature take its course.