I think its Ryan, (whitneys brother) he lives with janine so could have planted the ring there, he worked at the vic so could of easily got the key cut (as they showed last nights episode) plus if hes living with her, it would have been the easiest way to attach it to the rest of her bunch of keys!
Also i think he is actually in love with janine, and was angry with the way archie treated them!!!
Gotta be!!!!