A distinctive ring was taken from the Alexandra Hospital at about 1.45pm on September 21.
The owner took it off to wash her hands in the ladies toilets, opposite the coffee shop.
She realised when she got home she had left it on the sink and called the hospital but the ring had gone.
It is described as being in the shape of a coiled snake with the finger fitting up through the middle of the coils and the snake's head had a diamond in the middle.
The ring is made of yellow gold and is of great sentimental value.
A police spokesman said: "It's possible someone took this ring intending to hand it in and hasn't got round to it yet, in which case we'd appeal to them to contact us.
"We'd also appeal to second-hand jewellery and antique shops to look out for it in case someone tries to sell it."
Anyone with information is asked to call Redditch Police on 08457 444888.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article