With regard to burial, Thomas was buried at his 'Gardner' Hill. But, his bones and those of a slew of others were scattered to the wind, later. https://thomasgardnerofsalem.blogspot.com/2019/01/29-december-1674.html
A descendant of his son, Samuel, sold the land (Harvard guy, didn't need the money) that had some verbal agreement attached to it. This was when things were popping in the area due to people needing shoes. A descendant of his son, George, visited the place not long after and wrote of his findings (stones moved, some broken, no idea as to where graves were - as in, not an archeological site - rather, capitalism at its finest). Later, Sidney Perley, great asset to Essex County, noted that some bodies had been moved to the Trask plot (still there). We're trying to track that down.
Too, we want to do a virtual cemetery. I want to talk to people who grew up there about the terrain as they remember. I found this painting of the view from Gallows Hill that would have been about the same elevation. We're talking a 'U' shape. All of this can be studied with records. It's an on-going project. Too, there were some court proceeding about the whole affair.
But, it turns out that little Essex County, of such note, has hundreds of instances where graves and bones were left unlabeled through movement of stones, in some cases, many times. Too, at this site right on the line of Peabody and Salem, they scarfed the terrain to improve movement (commerce essential). You know, we see this all of the time with highways cutting through the landscape.
An ironic twist. Looking at the site via Google, it looks as if the little cemetery that was disturbed is now covered, in part, by a building, the Holy Ghost Society. That, to me, is Thomas' response.
I first asked the question of the burial in 2010 at Harmony Grove, itself and several times after when talking to people. Never got a good answer. So, went looking. There's more to do, but it's on the stack like a lot of other stuff.
BTW, after taking a further look at the FindAGrave, I'll suggest edits to make it more of an asset. Sometimes, it's easy to get changes. Not always.