Original desktop gone and replaced

Hi

Can anyone help?

I have a 27" Mac with OS High Siera version 10.13.4.

This is my home comp.

I ran an update yesterday.

When the comp rebooted it came up with the desk top of my work comp and all icons and information such as iweb with websites, documents, etc, have gone.

I rebooted again and this time the desk top for my Mac air laptop came up as my desk top.

I contacted Apple but they could not help.

Help appreciated.

Thanks

Graham