"I have a lot of handbags, so I thought I'll use the one underneath all the rest thinking 'if it's not used it will tear and rip'," she said.

"I just opened one of the side pockets to put my phone inside and found an envelope in that there was $5000 in $100 notes."

The last time the college teacher had seen close to that amount was 20 years ago, when she had first migrated and needed to pay about $1000 in rent.

Ms Ambrose bought the simple black shoulder bag in 2019, but couldn't recall where she bought it from. She was relieved to see the envelope also contained a withdrawal receipt with a name at the top.

"I was feeling so guilty that it was in my cupboard for so many years. That person would have been in agony for that money," she said.

She was surprised no one had checked the bag's pockets before selling it. She immediately took the money to Tuggeranong police station and told police everything she knew about it.

"I was not at peace," she said.

"[Police] told me after three months if they didn't find the owner they would return the money to me. But I was really praying they should find the person. I really didn't want that money because it was not mine, it was someone else's hard-earned money."

A few days later, Ms Ambrose heard back from a police officer. The person named on the bank slip had been found and the money rightfully returned.

She said the owner was an elderly widow and a cancer patient who knew she had lost the money, but eventually stopped looking for it.

She said the woman, who was in need of money to pay for her intensive treatment, was "shocked and overwhelmed".

The Canberra Times understands the original owner preferred not to speak publicly.

Ms Ambrose, a maths and science teacher at Erindale College, was beyond delighted she was able to make things right and, at the same time, set a positive example for her school children.

"Honesty and trustworthiness - these are all the things which we teach students," she said. "Honesty is the best policy."

Speaking of well-meaning strangers, only last month, a bike shop gifted a brand new bicycle to a teen who had his stolen the same day he bought it.