If they got into the water jacket of the block, it is very unlikely that they will come back out. They can get lodged in-between the bores or at the bottom of the water jacket. Then would have to climb back up to get through the timing chain cover to the water pump again, and I don't think that there is enough "current" to pick them up and find the hole...
They will probably be tricky to get out if you had the block torn down with all of the freeze plugs out...
