As the QC has been knocked back, wait 6 or 7 days and see what they do, if more QC's then do the utmost to find the Q. For insurance make up a nuc with her if you have enough bees. If you leave Q & QC,s the likelihood is high they may swarm thus depleting colony numbers.
If in 6 in or 7 days time you find more or another QC you should be able to age it dependant on if sealed or unsealed. A sealed cell will likely mean it is 9 or 10 days old and unsealed cell 6 - 8 days old depending on the larva size.
Then one will have a more exact date of when she will emerge. One can leave 2 or 3 cells to develop until day 13 or 14 when then it is a best to select just one nice cell and either harness the others or destroy them.