How do you think Samsung removed screen without cracking it.

I own a Mobile Phone Repair Company in UK - Phone Repairz NE Ltd

I recently sent my S6 Edge to Samsung as the Home Button stopped working and this was under warranty and to repair myself I would of need to replace screen as removing old one would of been damaged. (Free Repair from Samsung much better)

I put a light mark on my screen before I sent it, because I obviously suspected I would get a replacement screen in order to replace the home button. This was not the case. When phone returned and I inspected it, there was a New Home button and my original screen.

It was sent to A NOVO UK LTD, Norwich.

I have always believed you could not remove the screens really without cracking it etc.

I would love to have some inside information on the machine they used to remove this screen without cracking it!