What made Jem scared after he went back to retrieve his pants?

Jem was frightened by the fact that they were mended and folded.

His pants were mended and folded and he said that it freaked him out because it was like someone knew he was going to come back for them. Turns out Boo mended them.

Boo Radley mended Jem's pants after Jem went back to retrieve them.

Thanks Aylin, Jill and Yamquzzuhalamma!!!!!!!!!!