A shar-pei crossbreed named Kai was found tied to a railing outside Ayr station in Scotland.
The Scottish Scotland's Animal Welfare Charity (SPCA) is appealing for information.
"Regardless of the act, Kai was left with his belongings, this was a cruel incident and we are keen to identify the person responsible," a statement from the SPCA said.
The suitcase held a number of the dog's belongings, including a pillow, toy, food bowl and food, The Independent reported.
Abandoning an animal is an offence under the Animal Health and Welfare (Scotland) Act 2006 and anyone found guilty of doing so can expect to be banned from keeping animals for a fixed period or life.
"This case highlights the potential consequences of selling an animal online as it often leads to the impulse buying of pets that people know very little about," Taylor said.