I would login to network router and look at list for all network devices. Alternative, you usually can see all the network devices from clients running Windows or MacOS, etc.
If I could not do that, I might determine IP of my current device increment +1 and try each IP address individually. Assuming you used DHCP, the typical algorithm allocates IP addresses sequentially. For example if my current device had an IP address of 192.16.0.24, I would type 192.16.0.25 into my browser and see if I get a login prompt back, rinse and repeat 192.16.0.26...until you find the NVR.
This also assumes you know the an id/password for the NVR.