回复：回复：两个关于骗子的疑问， 有人可以帮忙解释一下吗？谢谢

Another likely possibility: it sometimes takes long time (more than a few weeks) to truly clear a check, even the money already shows on your account now, the bank can take it back if it's identified as a fraud.

Paypal dispute is fairly common, for your second case.

Google your cases and you will see lots of discussions.