How to find current phone numbers?
Even when I know the name and address of someone, it is nearly impossible to find their current phone number (in the USA). People search sites will give up to a dozen numbers for a particular name+address, but usually all of them are discontinued. If people don't maintain LinkedIn/Facebook/Twitter activity, how can you contact them?
At this point, social media is the wayto get ahold of people. Not having social media in 2023 is like not having a phone number in 1990
Write them a letter and ask them :)
How often do you have this problem? The easiest solution might be to mail them / show up at their door (startup idea?)