I've noticed the same behavior and have the same problem, its a no-go with the information being deleted. Have the user set the IP to "Reserved" not "Used". That seems to preserve the information.
this is the correct answer that fixed our problem
IPAM is designed to scan the subnets you enter. When an IP cannot be "pinged", it assumes there is nothing there and starts a "Transient" timer. Once the timer hits is end, it will mark the IP address as available. To resolve this, you can edit the subnet properties and scroll down until you see the picture below. Check the "update but not erase manually entered data" if you want to keep stuff you entered that the scanner could overwrite. Under Transient period, select unlimited duration. This will prevent it from marking it as available if the IP is not responding.