In (Kanazawa, 1998) it was shown that rigid Classical Categorial Grammars are learnable (in the sense of (Gold, 1967)) from strings. Surprisingly there are recent negative results for, among others, rigid associative Lamb ek (L) grammars. In this paper the non-lcarnability of the class of rigid grammars in LP (Associative-Commutative Lambek calculus) and LP0 (same, but allowing the empty sequent in derivations) will be shown.