Report loss of old BRP card

Hello,

I lost the old BRP card that I was required to return upon receiving the new card. I read on this forum before that when someone reported the loss of their old BRP card after receiving the new one, the new one subsequently got cancelled by mistake.

On the online report form it says "BRP number" is optional. I'm a bit worried that even if by putting in the old BRP number it would still have the new BRP card associated to my name cancelled. Could I check whether anyone has been in a similar situation and successfully had their old ones reported without getting the new card cancelled?