Some things seem impossible to forget - yet one bus passenger left an improbably large painting behind while on public transport last month.
It was just one of around 1,900 items dealt with by the lost property office in Dublin Bus every month.
Joe Elliott and the Dublin Bus team at Earl Place in the city centre, where the lost property section is located, said an increase in passenger numbers has seen the amount of items left behind rise dramatically.
More space had to be added to hold all the bags, suitcases and plastic bags left on vehicles.
Passenger numbers on the fleet have risen by 10 million this year.
Among the items in the lost property office when the Irish Independent visited were a baby seat, buggies, and "loads of scooters".
"A lot of suitcases get left behind, mainly by people on the way to the airport. The lost property office often gets calls from people who have returned home from abroad, and are seeking the return of their possessions," said Mr Elliott.
Meanwhile, when it comes to cash in wallets, he said: "The average amount would be €40 to €60. It all depends."
Keys, glasses, umbrellas, students cards, leap cards and PPS cards are often left behind.
The retrieval fee for people reclaiming their items remains just €2.
In terms of musical instruments, "it's mostly guitars that get left behind on the bus, but we have had ukuleles," said Mr Elliott.
While people tend to collect items like wallets, there are many items that people never bother to reclaim.
"Unclaimed mobiles go to the Jack and Jill Foundation," said Mr Elliott.
Meanwhile, the clothes that are suitable go to charity after a month of being held in the lost property office.
However, valuable items like laptops are held for longer than that.
"There are a lot of people who are taking our advice in relation to putting phone numbers on school items now," said Mr Elliott.
Items found on buses are logged in the garages and then brought into the Earl Place office, where they can be collected the next day from 1.30pm onwards.