Uh-oh, April Fools joke gone wrong?

Yesterday morning I proposed to my long term girlfriend as an April Fool's Day joke. She was so, so excited, she immediately whisked me to the bedroom and boned the **** out of me. I was thinking 'yeah man this is bloody great' but when I told her afterwards that it was only a joke, a prank, a false proposal I think I watched her heart break in half in her chest. She immediately fled the flat we live in and I haven't seen her since. She isn't at her mums and she didn't take her car. WHAT DO I DO?