Thirsty after his long journey, he pulled up outside the Rising Sun Hotel to stop and quench his thirst.
When he came back out, he found three of the gum tree seedlings had been pinched from the wheelbarrow.
The three stolen gum trees were planted around Greytown with the one surviving outside St Luke's Anglican Church.
Mrs Connelly said it was a pity that someone had written on the sign as a lot work and money went into putting up the sign. Hopefully the writing could easily be removed, she said.
"It's quite understandable that someone wants to point this out but why don't they come to us instead of writing on the sign?"
The trust has gradually been replacing the old green information signs around town over the last few weeks with new signs.
The sign by the historic tree was reprinted from the old sign as it was getting faded and difficult to read.
She said some of the finer details on the sign could be contentious and people could get upset, especially if they were descendants. "This person questioned the number of gum tree saplings Samuel Oates brought to Greytown, and took issue that we didn't mention he brought the mail with him."
Mrs Connelly said another issue with historical signs was there was a limit on how many words could go on the sign. "If it's too long people won't read it so you have to keep it short."
Mrs Connelly, a former archivist at the Otago Settlers Museum, said the early history of small towns often didn't have written records.
"It's not easy for such small places, beyond rates documents, there's not a lot," said Mrs Connelly.
A book republishing the letters of Mr Oates' wife, co-authored by Mr Oates' great great grandson Allan Farley, did help document what happened around that time.
"There are certain things we know because she mentions them in the letters."
Mrs Connelly said oral histories could sometime clash with one family saying one thing and another disputing it.
The best way around this was for the wording on heritage signs to allow speculation, she said.
She said the trust had no calls or complaints about the new signs since they went up.