In WoW, if you engaged in a trade transaction through chat, and you are ripped off, and you report it, there will be an investigation and if the investigation shows you got ripped off, you will get your items back and the offender will be punished. I know this as fact as having had it happen to me. Chat logs showed what was agreed to and trade logs showed what was traded.
It is little different than agreeing to a loot system in pre-made groups only to have the loot distributor go against the agreed upon rules and give an item won by roll to his buddy instead of the roll winner.
Simply put, a system IS in place in WoW to prevent these types of actions.
In WoW it is common to see people in the chat requesting things be made by complete strangers, saying "have mats", meaning that person will provide the crafter with the required crafting materials. And that's because Blizzard enforces the idea that players are entering into a contract by agreeing to craft something for someone and taking those materials. Eventually I'm sure they'll implement a mechanic to automate the crafting without any risk, but until then their GMs act as arbiters.
Personally I doubt SWTOR GMs are not allowed to intervene in this type of case, and to the OP I would suggest trying to report this player's behavior again. CS in this game is very hit or miss, with some of the CSR not even bothering to read past the first couple words of a ticket, or cherry picking out key words like a bot.
Make sure to ask that they check the chat log with an approximate time when it happened, location (zone and server), what chat channels were used (general, trade, whisper, etc.), your character name, their character name, and the name of the item(s) that were transferred. If you get the same response, request that your complaint be escalated, and include all previous CS ticket numbers in that request.