@morgentown said:

8/2/98 Ghost - Deer Creek (now Klipsch Music Center)
12/8/99 Piper - Cumberland County Civic Center (now Cross Insurance Arena)
6/30/00 Halley's Comet - Meadows Music Theatre (now xfinity theatre)

-All in venues that have since changed their names and that Phish has played this summer!

Well done! The Ghost was easy for me to find. Then the Hint came. Fortunately I knew it had nothing to do with the Simpsons Secret Language since none was played in the 8/2/98 show. Thought perhaps all jams were from Deer Creek (given the name change). Also thought the hint could mean the jam was always the preceding song before ____. Which given I knew the Ghost would have been Lifeboy. So searched 97-00 Lifeboys and started listening to jams leading into it. Finally decided it could just mean the venue changed its name and gave up given there are way too many name changes these days.

Again, great job and thanks @ghostboogie!