Odd slug
 

This morning ( about 5.am) I found a 3inch long black slug (?) climbing up
my cucumber plant in the greenhouse.

When I got it off ( it was stuck fast and a bit difficult to remove) its
front end was a bit odd in that it was all mouth ( just what appeared to be
a gaping hole at the front, no little horn type things a etc).

Anyone seen anything like it?

Was it possibly what I think it might have been - and if so , how did it get
there ? Suggestions welcomed.

Thanks.

PS - I killed it by cutting it in half with a pair of scissors. So I do not
have it as a specimen