Temp folder location? Transfer never showed up

So its my understanding that multiplicity uses a temp folder for copy/paste/transfer operations.
 
its also my understanding that no file size limit exists.

I tried to copy/paste a ~4GB iso from one pc to the next, and while the transfer did initiate, and showed ~8MBs which led me to believe it would take roughly 10m.   I went afk.  came back and the bar was gone so i had presumed it finished but the file was nowhere to be found. 

a quick google was sprinkled with issues about this happening and files being left in the temp folder needing to be manually cleaned up.

with something that big, i want to make sure first and foremost no remnants exist.   second, understand why it didnt work properly?  It certainly does with smaller stuff.