Accessing PC with local IP but physically on a different subnet

Subnet A: 192.168.3.0/24; Subnet B: 192.168.20.0/24. Set up a server while physically on subnet A and assigned temporary IP 192.168.3.4. Later server was moved to a remote location which is on subnet B. However, I forgot to change server's IP to that of subnet B 192.168.20.4. I don't want to give out admin's password to anyone on B to get server re-ip'd. Subnet connected via VPN. Is there any way to get to the server 192.168.3.4 in this scenario. VPN routers have multiple interfaces that can support different LAN IP subnets. Site A has a second ISP. Thanks. Alex.