Valentines problem - in relationship but received card from someone else

I know this isn't a serious problem but its stressing me out and I'd really appreciate any advice. On valentines day, I received a card in the post that was not from my partner. I was really freaked out because I've never received a card like this since I met my partner over 11 years ago. The card said it was from a very secret admirer who sees me every day and would love to take me out for dinner some evening. I've thought long and hard and the only person who sees me every day and doesn't know I have a partner is the new postman! I decided not to tell my partner about it as he's always been paranoid about other men and I thought it would only stress him out and ruin our valentines day together. Also, if the same thing happened to him, I'm not sure if I'd want to know. I spoke to a friend and she said I should be flattered and just ignore it as its only a bit of fun. I know my partner wouldn't find it funny but am I doing the right thing not telling him? Has anyone else ever got a card like this? My partner and I aren't married but now I'm thinking I should wear a ring to put others off. I'd really appreciate any opinions. Am I over reacting?

Yes, it's an over reaction. You are in a state of hallucination. Come out of it immediately, before it's too late. Donot ignore the present and run behind assumptions.

Just throw the thought along with the card out of your mind and house and continue with your life. In case ever he finds out...just tell him you felt it was someones prank and not worthy enough to waste our time on it.