When I try this trick, it just doesn't find the collision. even when it should take just a second, it never finds it. can you confirm these are the steps you did?
Choose a range (say, 48 bit)
Choose any key that is not in that range
run kangaroo on it for some time, (with -m 3 to be exact to your example), and make it save the work into a workfile.
Then load the work file into a new session with an actual key inside the range.
This is what I did, didn't work.