If cant take the rocks out,drain the water out some until fish goes in open water and use 2 nets to try capture is one method.
Another would be sticking a plastic bag inside its favourite hole it bolts into when scared,obviously need it be out hole and in open first so try distract it or male it go In another hole then wait till it comes out and then go to catch it with net,hopefully it darts into its favourite hole now inside the bag ( leave little excess bag flaps sticking out so can quickly grab bag out hole carefully)
Another is putting food inside net to feed the fish but this can often take time and I know time is against you.
Some kind of fish trap .
I got 2 blennies and a cleaner wrasse that hide/ dart/ sleep in the tiniest holes ever,literally just big enough for them to squeeze into,I dred the day if I ever need catch them and I made 2 big large glued/ mortared rock structures in my tank with lots of caves/ tunnels and such so less stressful for fish but perfect for them to evade me if ever need get them out ha ha
Another option is wait till night time and use a red light so you can see but apparently fish don't see to well or quickly turn on a flashlight to startle them then net them quickly but a fish that hides in rocks this not going to work pfffft
Anyway good luck getting them out and if cant get them out, unfortunately I know you say taking rocks out isn't an option but maybe the only option,some have mentioned about lifting rocks slowly out water so fish slowly goes to bottom of rocks closer to water till it then jumps out but be weary that fish doesn't stay in rocks and you have fish in rocks out water to long