I think the answer should be yes so that those taking investment should feel pressure to ensure that the money from investors is legitimate. Otherwise, it's going to be "whoops, we didn't know ;)" every time.
There seems to be a false dichotomy here between either “always treat the recipient as guilty” and “just let them claim ignorance without questioning it”.
I don't think you should treat them as guilty if they took funds that were stolen, unless you knew for sure that they knew. Just that they should always have to give it back.