Caselaw - capital - states unaware of investment

Is anyone aware of any caselaw relating to a claimant not declaring capital in a means-tested benefit application because they had forgotten about the investment?

In my case it seems likely that the claimant would have participated in money-laundering checks when the investment was made but then forgotten about it until some later date when they discovered paperwork about it and cashed it in.

I know that I’ve previously worked on the basis that a claimant cannot declare something they don’t know but it seems like they did know and then didn’t.

(For what it’s worth I believe that they didn’t know when they made the application - mostly because I believe they’d have accessed it sooner if they’d remembered about it.)

Any thoughts?