If a debt has been paid within the time prescribed in Section 9154 but without a claim having been filed and established in the manner prescribed by statute, in settling the account the court shall allow the amount paid if all of the following are proven:
(a) The debt was justly due.
(b) The debt was paid in good faith.
(c) The amount paid did not exceed the amount reasonably necessary to satisfy the indebtedness.
(d) The estate is solvent.