Yes. Merge the new ticket to the existing one and reopen the ticket and inform the ticket owner.
Example given:
Gen CS A is still working on an unresolved HCN request but he/she resolved the ticket prematurely. Gen CS B received a new ticket for the same booking asking for a special request. Gen CS B can merge the new ticket to the existing ticket of Gen CS A.
Note: If the case is urgent and the original ticket owner is from a different shift, merge the ticket and make sure to work on the case accordingly.