Since the bolt was forced open in order to pass the strick when you closed the top,a thin putty knife should push the bolt aside.

The model I had had two opposing latches, so I bolted two hacksaw blades together, inserted one side of the "V" on each side of the latch and by squeezing them together with a plier, released the latch.

You should be able to find a solution vie google, as well.

I'd want to find a way to pick the lock. (That could damage it, of course, but it also might not--a hacksaw would mean you needed to replace it.)

I'd send my 16yo over to try it with his lockpick tools, but...

In your shoes, I'd call a locksmith, to be honest. He (or she) could get it open without as much damage. And then I'd ask them to make another key.

"a hacksaw would mean you needed to replace it."

However, two blades bolted together on one end creates a "V" shaped tool, that when compressed releases the "opposing" latch catches.

"In your shoes, I'd call a locksmith, to be honest. He (or she) could get it open without as much damage. And then I'd ask them to make another key."

Open the lock remove the portion in the tambour and take it to a locksmith saving yourself two call fees.