I've personally encountered this a lot as I RP a decent amount. Truthfully, if you're RP'ing you have to expect that others may misuse the information.
However, since you sent the RP, other players will know the information. If people were punished for acting on it, they could be punished unfairly if a player is intentionally not trying to act on it, but still could be accused as such. So, in general yes you can use the information, but it is considered bad form unless you have some backing for it.
Just be aware if you write out someone's private thoughts, you better have reason as to why you think they did something or you could easily be accused of all sorts of stuff IC. OOC, you're safe from being banned for meta-gaming.