Hello there and welcome to BYC!
Yes, they can become this traumatized and will stop laying until they feel comfortable in doing so. Obviously yours are still in shock. You might help move them along a bit with feeling relaxed. I have found these first two things to be very comforting to traumatized chickens....put a ticking clock in the coop. Let it tick away night and day. The constant white noise the clock gives off will help lower their blood pressure and stress. Next put a radio in the coop and set it to some soft quiet type music. Calm music is very relaxing to birds and will help relieve stress. Turn it off at night. I have used both of these on birds with high anxiety with good success.
Next, I would go sit with your birds. Is your coop a walk in type? If so, bring some goodies along with you and sit on the floor with them. Take their minds off their troubles with some goodies. Let them climb all over you, sit on your lap. And if they are too frightened to even do this, work with them every day to get them to this point. Sit with them for 20 mins a day. Every positive experience they have with you will help them bond better with you and trust you when you tell them all is well. Eventually you can coax them out of the coop. Don't force them out, this will only cause more trouble.
Next, put some fake eggs in the nest boxes. A hen feels confident when she sees that another hen has laid her egg there, so if it was safe for her, it will be for this hen to lay hers.
Now being that this is a low light time of year and chickens laying hormones work on the amount of available daylight, your birds may be holding off on the eggs for this reason as well. You might try some added light in the coop, maybe an extra 2 hours in the evening and an hour earlier in the morning. About 12 to 14 hours should help to get them laying too. Always give them at least 8 hours of complete darkness.
Good luck with your flock! Eventually with these techniques, you should get them back on track! :-)