At the end of Buffy the Vampire season five, which was also the ending of the WB run of the series,
The episode concludes with a shot of the clearly-marked grave.
When the show returns in season six, several Buffy-verse months later, we find that the gang has cleverly
re-purposed Spike's Buffybot to fool Sunnydale's vampires and demons into thinking there was still a slayer in town to maintain order. It was even hinted that Buffybot was used to fool Buffy's father on the telephone.
If this was the gang's strategy, why did they leave a marked grave in the cemetery? Since Sunnydale gets unusually high cemetery traffic, wouldn't the lie have been exposed very quickly?
I know that season five was originally intended to be the last of the series, but UPN had already picked up the series to be continued in the fall of that same year. The same writers and producers stayed on for the UPN seasons, so I have a hard time assuming this is an unavoidable plot-hole resulting from the series' being resurrected well after cancellation. At the very least, the gang would have had the headstone removed by the beginning of season six (but we see the headstone is still in place when they go there to perform a ritual).
Is there another plausible explanation?