The spell Locate Object says:
You sense the direction to the object’s location, as long as that object is within 1,000 feet of you.
The spell Polymorph says:
The target’s gear melds into the new form. The creature can’t activate, use, wield, or otherwise benefit from any of its equipment.
If the object targeted by Locate Object has been "melded into the new form" of a polymorphed person will Locate Object succeed?
On one hand you could say the item, eg a spear, temporarily doesn’t exist and so cannot be located.
On the other hand spells only do what they say they do and Polymorph does not say is hides items from being detected.