Months after sending a check from maaser money to a charity has still not been cashed? Can I now donate the money elsewhere?

Several months ago I sent a check to a charitable organization using maaser money. It is now several months later and the check has not been cashed.

Can I use this money to send a donation to a different organization?
Am I required to follow up with the original organization as to why the check has not yet been cashed? Maybe they simply misplaced the check.

I understand in my scenario I can easily call the organization to ascertain what transpired and clear this up. This incident had me thinking though, what about a case where I don’t know the poor person I donated to and therefore I’d be unable to follow up with them about the check. What would be my obligation and what do I do with the maaser money still in my bank account?

From a Halachah perspective, you are not required to pursue the organization you donated to. It’s their loss.
However you may want to consider following up with them, if you feel you donated to an important cause. If you feel for whatever the reason that it would be better to give elsewhere, that’s ok.