Rescued My Baby Shrimp

Hello all and a Happy Newish Year!
Well as my shrimp tank was showing a slight trace of ammonia I decided (despite no gravel cleaner as it's given up the ghost) to do a water change, placing the pump, filter sponges etc into the waste bucket and pouring the waste water on top of them

I jugged the water into a clean waste bucket using a white jug and checked the jug water very very carefully as i remember Sue saying that on a number of occasions she's had to rescue shrimp from the change bucket.  I can be 99.9% certain that there were no shrimp in the jugs of waste water.

I didn't think to check the bucket until I'd taken out about 7 litres of water and was amazed to see at least 10 shrimp swimming around, not new borns either, although nothing like full grown.

Now I did look at the filters etc before I popped them into the bucket and there wasn't anything obvious on them, so where did they come from

I do have black sponge strips on the edge of the filter compartments (which I put there originally to stop the endlers that I had at the time from jumping into the space there) and again I'm sure that there wasn't anything on them.

I know realistically that they must have been on one of the sponges or filter cloth but I don't see how I could have missed them.

They aren't a bright red but they had enough colour for me to see them at the base of an orange bucket.

The only thing that I didn't check was the pump as I couldn't get it open (fingers aren't good today) but I did check that compartment and surely if they were living in the pump, which is extremely powerful for a 22 litre tank I would have seen some left in the water after the pump was removed. Could shrimp, little ones at that, live in a powerful pump without being mashed up?

Thanks Sue.
I'll have to be more careful next time, especially as I'm hoping to replace the gravel cleaner soon so am likely to "hoover" more of them up.