Only laid one egg?

[Lacybug]

Ok, so my zebra finch hen laid an egg about 4 days ago, and hasn't laid any since. She does have a male in the cage with her, and I have seen mating attempts, but she's still very young, and I can tell they're.. inexperienced so it might not have been "successful." I really don't think she's egg bound, as she's not showing *any* symptoms, and is acting completely normal and active. Eating, drinking, flying, jumping, peeping, etc... They also eat a healthy diet including oyster shell, cuttlebone and egg (including shell).
I've left the one egg in the nest, and can see in completely so I'm sure there aren't any more. No others on the bottom of the cage or in food/water cups either. I also highly doubt they've eaten any.
The day before the egg appeared, the finches had to be taken in the car, which was a stressful situation for them. So my question is, is it possible for a hen to lay one dud egg, and then stop? Or stop the egg laying process due to stress?
I'm getting Calcium Plus right away to have on hand just in case.
Thanks for any ideas!

[Corkysgirl]

It's always good to have the Calcium plus in case of emergency egg binding. Yes it's very possible for her to stop laying because of stress. I'd just leave the egg and see what happens. It's probably not fertile but she may go in and start laying again. She'd lay 3-4 eggs before she'd start sitting on them to incubate. If the one isn't fertile, no harm leaving it. Make sure she has plenty of good protein, salad, vegetables, etc.