Follow-up: Eventually, I used my wife’s phone to reach the support desk. After all I managed to re-login. It seems I was using the wrong from my two phone numbers. My bad, but I hope Revolut will improve user experience in such situations. Ability to chat with the support desk directly from my phone would be appreciated.
Note also I sent the email to feedback@revolut.com. In the automatic reply, they asked me to either use chat, or “if you are unable to reach us via in-app chat, please reply to this email and include the phone number you use with Revolut.” I didn’t do it since the problem got resolved in meantime, but it might be an option for somebody who can’t use somebody else’s account to reach the support desk.