As we are unable to write temporary files to the Steam install location for GameMaker: Studio, you won't find your traceIDE.log inside the installation folder like you would in a standalone version of GM: S. Also, as we have to deal with the possibility of different Steam users and different Windows users, we've had to use a system where your files relate to you individually (but not in a plaintext way) and are in a protected location.
Therefore, if you are asked to provide a traceIDE.log from a Steam install you will find it at C:\ProgramData\gamemaker_studio then in a subfolder which is an MD5 of your Windows username (a long folder name of seemingly random characters). The easiest way is simply to check the timestamps for any log files and see which file most closely matches the time of the incident.
Please be aware that C:\ProgramData is a Windows system folder and so will be hidden by default. You will need to "Show hidden files and folders" ("Show hidden" in WIndows 8) inside Explorer in order to see the folder. Also, please note that if you try to move/delete any files inside this system location you will need to provide administrator access.