If you slip out the back to terminate your lease early, you may not be able to get your security deposit, and furthermore, you may still owe rent after you have gone.
If you hop on the bus and do not leave a forwarding address, it will be difficult for your landlord to send you your money (or notice of what happened to it).
The answer is easy if you take it logically: Landlords have fifteen days to return your security deposit. That gives them the opportunity to examine fully the property for damages. Then, the landlord has up to 30 days to send you written notice after you leave to tell you they are keeping all or part of your deposit. If you think that is a dirty deal, you have 15 days to notify your landlord in writing (Certified Mail, return receipt requested).