Full Idea
If one came to believe p with good evidence, but has since forgotten that evidence, we might think one can continue to believe justifiably, but evidentialism appears unable to account for this.
Gist of Idea
Evidentialism can't explain that we accept knowledge claims if the evidence is forgotten
Source
Daniel M. Mittag (Evidentialism [2011], 'Forgotten')
Book Reference
'Routledge Companion to Epistemology', ed/tr. Bernecker,S/Pritchard,D [Routledge 2014], p.173
A Reaction
We would still think that the evidence was important, and we would need to trust the knower's claim that the forgotten evidence was good. So it doesn't seem to destroy the evidentialist thesis.