How to file bitcoin income to the IRS as a nonresident alien
The analysis is the same as for other property.

You only need to report income that is effectively connected to the US or that is fixed, determinable, annual, or periodic (FDAP).  So while you would need to report a US-sourced scholarship grant or wages from working in the US, you do not need to report a foreign transaction.

If the transaction was a foreign person abroad (your husband) buying and then selling from foreign people, and the property was not located in the US (this is mostly about real estate), then you should be quite safe not reporting it.  The fact that he sold it for USD does not make it reportable or taxable in the US.

Please review Publication 54 if you have further questions.