Thanks for posting your query at DoctorSpring.com
I have gone through your question in detail and I can understand what you are going through.
Its ok even if you have by-mistakenly taken concerta at night. Mostly it wil not lead to any problem and you may still sleep well. If you have xanax with you, you may take your xanax as well.
Earlier it was strictly mentioned that concerta should not be used at night. However recent research has stated that giving concerta has improved the sleep quality as well.
So not an issue. Keep calm and take your xanax (if you have it with you) and try going to sleep.
Hope this helps,
If you have any further query, do let me know.
Dr. Srikanth Reddy