The 52-year-old vanished from her antiques shop in Llangollen on June 16, 1990.
And now 25 years on, her brother Leonard Davies, now 71, says he will never give up hope that his sister will return home.
Mrs Evans, who was married, put the note up in her shop, Attic Antiques, just before 1pm and was last seen outside her home in Market Street at 2.30pm.
Mr Davies said: "I've heard nothing at all in the last few months, not a thing. But to be truthful I have never given up.
"I have never lost hope that something will turn up. This is a difficult time of year and I have been thinking about her all week.
"I still think about Trevaline a lot and still miss her very much."
He added: "I remember the Saturday she went missing as if it was yesterday. If you asked me what I'd been doing a fortnight before, or even yesterday, I couldn't tell you.
"But that day, I'll never forget."
Her husband, Richard, died last year without ever knowing what happened to his wife.
On the day she went missing, Mrs Evans left Attic Antiques, on Church Street, at about 12.40pm, leaving the note on the door.
At about 1pm, she bought an apple and a banana and was seen crossing Castle Street.
It is thought she may have returned to her shop at this point as a banana skin was found in a waste bin there, though it was impossible to know whether it was the one bought that day.
The last confirmed sighting of Mrs Evans was near her home on Market Street at 2.30pm.
There were two more suspected sightings later on the day of her disappearance, although both are unconfirmed.
Five minutes after Trevaline was seen on Market Street, a woman matching her description was seen walking out of town – along the A5 towards Corwen, beside the riverside park.
A further one hour and 10 minutes later, at 3.45pm, there was another sighting, this time of her walking into Park Avenue from the direction of the River Dee – and then she vanished.
Speaking in 1992, Detective Chief Inspector Colin Edwards, who was heading the continuing investigation into the disappearance, said: "It is without doubt the strangest inquiry I have ever been involved with.
"How a happily married woman could vanish without trace on a sunny Saturday morning in a busy town centre is totally baffling."
Her husband had been away during the week of her disappearance and was renovating the couple's holiday bungalow near the coast at Rhuddlan.
She had spent a couple of days there but returned to Llangollen on June 13.
When the case was reopened in 2001, the main focus of the inquiry was her movements in the days between her return to Llangollen and her disappearance.
An artist's impression of a man in a blazer apparently seen in her company was drawn up and circulated during the investigation in 1990.
However, it had failed to bring anyone forward and was later disregarded as no longer accurate by officers in 2001.
North Wales Police have confirmed the case remains open, but the investigation is not currently active.
Mr Davies is refusing to give up hope but said it was unlikely the investigation would be re-activated.
He said: "The officers who worked on the case at the time, the ones I got to know, have all retired.
"There are no new theories about what happened, or any fresh evidence, and I realise the police have financial limitations.
"I would like the investigation to continue, I am forever hopeful of finding out what happened."