"I couldn't find XXX" and "I didn't find XXX" which is better?

Question

We communicate via email. He told me to get something under an address. But I can't find it under that location.

How would I say?

I didn't find it.

-

I couldn't find it.

Answer 1

"I couldn't find it" is more appropriate for your case, I think.

"I didn't find it" implies that you chose not to find it. "I couldn't find it" tells the listener that you tried, but failed.