How long can I expect the bacteria to survive in my filter without power?

Came home this evening to find the temp in my main community tank a little
bit on the high side - this was the one that was the coolest in the last
blast of heat that we had.

Did a water change and then noticed that the outlet of my filter (Fluval 304
ext) was not throwing any water back in. We checked the inlet valve and it
was reasonably clear however unless we manually pumped no water was being
drawn out or put back in. We think that it might be the impeller as the
motor is working fine - no blockages coz we can pump manually. Anyway it is
turned off so that the motor doesn't burn out.

To protect the fish I have put in a Fluval 4 internal (fully cycled - it has
been hanging around in another tank for months after being this one
originally - so in action for at least 10 months).

We can't do anything about the external until some time tomorrow. So my
question is will any of the bacteria survive? or will I have to start it
from scratch again? It is still full of tank water.

Thanks
Gill