The $5000j note is kinda hard to come by, even in a cambio or bank. I asked for them the other day at NCB and they only had 4 at my teller. They are used mainly to pay large JPS bills and the like. They have a clear plastic window near the middle of the note, to differentiate them quickly from the $500, which is surprisingly easy to do.
When the $5000 first came out, pretty much every store in Negril posted signs that they would not accept the note and/or make change for it, but this quickly became a moot point since you never saw one in circulation anyways.