My advice would be to cancel all cards in the wallet just incase it has been lost outside, and stolen.
My mum did this yesterday, although we live 6 hours drive away, we were visiting, so helped her contact the bank.
Has your relative got any neighbours you can be in contact with, to pop in occasionally and keep you updated?
Or as mentioned, you need someone going in to check on your relative, like a cleaner or carer.
It is much harder living so far away from a family member with dementia.
Luckily my mum has two lovely neighbours who see mum a few times a week, then they will update me, which is reassuring.