A wedding dress, an antique typewriter and a wheelchair were other odd items of lost property mislaid on seats and in carriages by absent-minded passengers.
In total more than 6,000 items were handed in to rail firm CrossCountry in 2008, with mobile phones, books and umbrellas the most frequently forgotten objects.
The cat, called Holly, was left on a service in the Bristol area but later reunited with its owner.
Staff said the £30,000 of used banknotes were discovered in a green holdall and handed in to station staff to try and track down the owner.
Costly items including MP3 players, laptops and jewellery made the top 10 list of most common lost property, and travellers have been warned to check they have left nothing behind before getting off trains.
Andy Cooper, managing director at CrossCountry, said: "People leave all sorts of items on trains and this year we have found some very unusual ones, including baby buggies, shoes, designer handbags, cricket bats and even a wedding dress.
"We always advise passengers to check their seats and the areas around them when leaving a train, especially at busy times, to ensure that they have all their belongings with them."
CrossCountry runs several rail lines spanning the country, with services connecting Aberdeen, Penzance, Stansted Airport and Cardiff.
The top ten items left behind on CrossCountry trains were:
1 Mobile phones
4 Bags (handbags, hand luggage, briefcase etc)
5 iPod / MP3 players
7 Carrier bags / shopping
10 Wallets / pursesOriginal here