Both of these statements make sense. To be grammatically correct you need to split them as they are considered two separate and complete thoughts. (A complete thought= subject (s)+ action(a)).
I(s) have hidden(a) it somewhere. You(s) will never find(a) it.
You could also separate them with punctuation when writing (comma/semicolon) or a conjunction when speaking (and, but, however, etc) :
I've hidden it somewhere and no one can find it.
A side note, "can" suggests the object no longer exists, "will" suggests that the speaker is confident the object will never be found.