speaking from experience, it’s totally fine to follow up even after a bit of time has passed. especially if you both communicated about going out again in the future, it’s reasonable to expect a confirmation or some accountability if their interest has changed for whatever reason.
that being said, if lack of consistency becomes a pattern after reaching out or even after meeting up again, this indicates a deeper issue on the other person, and you’d probably be better off spending your time and energy on someone who will meet your need for communication and be reliable. you arent wrong for having the instinct to check back on plans that were made, even if tentative.