Any question answered...

An avenue worth exploring then. See if you can find/obtain any logs of online activity. Might be able to see where the process broke down. If it's a bank error then I can guarantee that payment will be reclaimed in no time. They're just being lazy.

Indeed - Branch and internet banking are often managed quite seperately - so its often worth phoning the internet banking helpdesk for problems like this (as the branch staff most likely won't have access to internet banking logs etc)