What do you typically feed your toads? Do you have any moss in your tank?

It doesn't look like it'd be a problem, whatever it is. If he can digest it, I'd say he's fine. If you noticed any strange behavior or change in appearance (not eating, dark color, bloating) before passing it, it may have caused a brief case of compaction, in which case it'd be important to find out what it was so he doesn't eat it again with more serious consequences. But if your only concern is just the appearance of the waste itself, I wouldn't be concerned quite yet. It could just be that while you were cleaning the tank a strand of fabric fell in. Perhaps it's a partially digested insect. Or, if you have moss, he ate it and it passed undigested with food. It could have been anything. Don't get too worried :P