Landlords expect you to come at them for the deposit. If you don't, it's a 13th month rent. The serious renters just treat the deposit as their 12th month rent, but if you didn't do that, or care about your reference, you sue for it.

IANAL let alone your L, but at this point, in my 42nd year of life, if I don't get my security deposit back, I drop a buck fifty and put a suit in process, fully expecting the landlord to whine at me and then start the actual negotiation.