Can mould grow on cupboards from water damage?

I am living in an apartment and there was black residue on my cupboards underneath my sink. It was obvious it was the result of serious water damage from the previous tenants. When I confronted my landlady she claimed that it was not mould and that mould does not grow on cupboards only on walls. Is that true, and if so can someone please send me a link to a legit website that says so so I can call her out.