Well... I'm willing to bet that if the bag wasn't REALLY securely tightened and hadn't been weathered that there would be a distinctive smell.

not to compare to a poopy diaper but I know that Hannahs diaper genie no matter how secure lets off some stank when diapers sit in there for a while before the bag is changed.

It's not like potpourri... if there was any way for the smell of a dead body to leak out I bet the meter man NOTICED it. it's not something easily hidden