Do you have folding rear seats???
If so, just pop the trunk and crawl in through the rear seats.... Not that I'm speaking from expierience or anything
What's your year, Make, & model.... I've never heard of a car that wouldn't let you use the key.
My 03 will let you in with the key, just the alarm goes off until you hit the button on the remote.
Curious to see what you've got.