Approaching late stages of £30 freezeout , i shove with

and get called by

who has me covered.
Board reads

, theres a cheer by the lady holding

and the other locals on the table. The dealer quickly gathers the cards and starts pushing all the chips towards the lady.
I immediately say its a split pot with one neutral guy agreeing , however the dealer and the other locals say its too late as the pot has been awarded.
WTF !! From going on our backs , flopping the board and awarding the chips took under 15 seconds.I ask for a manager and he too says once the cards have been retrieved and awarded the result stands. WTF !!
I can understand if i objected a minute or two later but this was as the chips were being pushed towards the lady.
I don't totally blame the dealer as he had dealt the same speed all night and on this occasion didn't see the split pot , however the locals all protested against my claim to the split pot.
Was the correct ruling given by the manager ?
What would happen in a higher buy in game like a £1k + game ?