"Every argument between them will end with "at least I didn't drop the engagement ring down the sewer grate", a twitter user BigJim wrote".
However, they continued looking for the ring even after the couple left Times Square and they eventually found it.
NY police are trying to find the ring's owners.
"She said Yes - but he was so excited that he dropped the ring in a grate".
The NYPD commissioner James O'Neill has also gotten involved, urging users on the social media site to "do your thing".
The man frantically lay on the ground and peered into the grate while his partner looked on in concern, but they were unable to retrieve the ring.
Police say they hope someone can help track down the couple so that they can return their engagement ring.
It doesn't show the moment the man pops the question but we do see him getting down on one knee in an attempt to find the ring.
New York Police have found themselves at the centre of a real-life romantic comedy.
"WANTED for dropping his fiancée's ring in @TimesSquareNYC!"