[mothered]

Today I received a phone call from a Walmart rep asking me to return the empty box to a nearby Walmart store. However, I am not home at the moment and will not be for quite a while.

You should've explained It to the rep.

Instead, I pressed the rep, and he told me that they are going to investigate the case for another 24 hours.

Due to your noncompliance above, It's probably why they're Investigating It further.

I was also wondering is there a cause of concern regarding this SE as I have already activated the airpods on my phone.

Most likely It's fine but for future reference, always wait until the claim Is finalized prior to using the Item/device.