Sorry to hear that! I would suggest you to call CIC/ IRCC via phone and explain them about the sitautuion. Ask them how you can fix this. Their number is 1-888-242-2100
In the worst case if you do not get much of the help or suggestion from IRCC, then I would suggest you to immediately write an Explanation Letter with explanation about what happened. Also in the explanation letter add the courier tracking number for the application sent to Mississauga (take it from your lawyer). It won't hurt to write 'I apologize for the mistake' statement. Also add your and your parents details in the letter i.e.
Sponsor Name:
Sponsor's Date of Birth:
UCI Number of Sponsor:
Father's Name:
Father's Date of Birth:
UCI number of Father (if available)
Mother's Name:
Mother's Date of Birth:
UCI number of Mother (if available):
Draft this letter immediately and send it via the fastest courier to Ottawa address.
Also a send the similar letter to Mississauga office, requesting them to forward the application package to Ottawa.
Again, IRCC might suggest you some other route, but in case they don't, Explanation Letter is the only route i could suggest you, may be other members have some better ideas. And get a refund from your lawyer for the screw up!