You suggested the US were lying about it avoid 'severe repercussions' or as some part of a game involving shielding Putin from reality.
What is more likely is that the USA lacked the right info, or had a lag in that info, or sought to disguise how much they really knew, or quite plausibly not wanting to be the ones to confirm it had sunk, perhaps as part of some etiquette involving letting nations confirm their own major losses first. Such etiquette is often going to seem rather bizarre given what else happens in war, and Im very far from being knowledgeable about such things, but I expect it exists.
I will still partially concede to your point, since the aforementioned etiquette is a part of diplomacy, and such diplomacy does have an 'avoiding severe repercussions' dimension. Just not quite the flavour of it that you were getting at. ie its more about giving Russia more control over the timing and detail of the announcement of the loss of this ship, rather than completely enabling Putin to totally deny that the ship was lost, or enabling other parts of the Russian regime to hide the truth from Putin.