(a) No, they should not modify anyone’s confidence that you have found your keys. The procedure for determining whether you are holding your keys is sufficiently reliable that there is no need to doubt its results. What the factors mentioned should affect is your (and others’) confidence in the efficacy of the procedure you used to find them. If you made 100 attempts to find your keys and 1 succeeded, this is weak evidence at best that the attempt that happened to succeed had a good a priori reason to.
1.
(a) No, they should not modify anyone’s confidence that you have found your keys. The procedure for determining whether you are holding your keys is sufficiently reliable that there is no need to doubt its results. What the factors mentioned should affect is your (and others’) confidence in the efficacy of the procedure you used to find them. If you made 100 attempts to find your keys and 1 succeeded, this is weak evidence at best that the attempt that happened to succeed had a good a priori reason to.
(b) No.