Sapling in the Strawberry Tub!

I found this in the Strawberry tub. 
Just like a Cuckoo in a Blackbirds nest!!
How did it get there? Who or what put it there?
Was it a Squirrel or Human? Why? Curious to see if it would grow?
Well it did & had I left it grow there it would have thrown all the Strawberry plants out of their tub!
Have you guessed what it is yet before looking at the extra photos? Shall I tease you & just not add extras until you've guessed & add them another day.
 Mmm! now that's good idea :) The day I find that someone has given me the right answer I will add extras for you to see the evidence :) 
Good luck guessing!