The boss lost the young man's 79 yuan. His belongings have been converted into part of his neighbor's change, so he hasn't lost them.

If you can't figure it out, you can actually operate it again. The boss left real change of 2 1 yuan. He gave all the lost 100 yuan to his neighbor, but he had 2 1 yuan in his hand, so he lost the real change he found, 79 yuan!