a simple matter to transfer all your data from one drive to the other, and as you were promised this would be done I'm not surprised that you're a bit put out - I would be pretty upset myself.
With the clarity of hindsight I'm sure you can now see the sense in backing up all your data files before you send any computer away for repair, no matter how trivial the problem might be. Most computer companies state somewhere in their terms and conditions that they cannot be liable for the data that's on machines sent back for repair.
The fact that you specifically asked for the files to be transferred, and that the company assured you they would do it raises an interesting question - are they now liable to compensate you for the loss of your data resulting from their negligence in failing to fulfil their promise? I'm no lawyer,and I'm not inciting you to litigate but you might feel it's worth following up with someone who is qualified to advise you.
The matter would probably hinge around whether you acted correctly in failing to back up your data, especially as the files were obviously of some value to you, and whether you were right to 'rely' on the promise made by Time, and what, if any, tangible loss you have sustained as a result of the loss of the files. The fact that you would have to spend a considerable amount of time recreating the work may have a bearing, but you'll need to get some professional advice.
All this may be unnecessary if Time respond as you would wish them to. Let us know what happens would you?