work experience evidence?

I did an unpaid internship last year for 1 month, it was good experience and a valuable addition to my CV.

I have lost touch with my contact at the company and the company doesn't seem to exist any more (it's based in the far-east whilst I'm in the UK so I can't be 100% sure of this).

I have a signed reference letter from the director confirming the experience and the dates as proof (with the company address/phone on it as well, but they don't work any more).

Would this suffice for an internship background check? Last year I got an internship at a BB with this on my CV but they did get hold of the contact and confirm it. This year is a tricky situation, I want to be sure it's okay before I send my CV off for this cycle of applications.