Zorro: In my experience, it is always prudent to "see" the POA to verify the authority given. I wouldn't rely on the signature being "notarized" - that just confirms the identity of the signer - not the authority.
hr for me: In refinancing, since your husband was a signer of the documents, a verification of his being alive was important as he had an obligation to pay the note (as did you). One can't borrow money if they are dead (although their estate can, but that is a different story). That issue had nothing really to do with the POA (or it's validity) but rather with insuring that the obligor was alive and could pay back the borrowed money (or at least was alive at the time of signing - so they would have a claim on his estate if he later died).
POAs are strange things - and the way they are drafted can make a big difference (general or limited, indefinite or for a period of time, regular or "durable") and the specific authority given (medical, financial, etc.).
When in doubt, DEMAND the POA and consult a lawyer to see if it covers the transaction at hand.