Client Internal Serial Number blank

I have a client that was accidentally deleted from CMS (via right click menu).  We turned the client back on, it eventually got itself back to 'healthy' status and is checking in and receiving tasks, but the 'internal serial number' field is still blank on the Identification tab in CMS.

We've tried running a Gather Inventory task with just Hardware selected, but the field didn't populate.  We tried another task with hardware, software, and file processes checked and still nothing.  On the client, we did a Basic Inventory and reset agent and nothing.

Anyone have ideas to get the data in CMS for this otherwise working fine client?

Thanks!