Last summer I went for a trip in the USA. They stapled the I-94 form in my passport and was suppose to return it within three months (I think). I left the USA after 2 weeks only and did not return since. However, I forgot to return my I-94 on time.
I returned the I-94 a few weeks later! Following the advice on this webpage, I did my best to give them evidences that I left on time. I could give them the contract for my lease, the bus ticket I bought to leave (my name is not on it) and a few signed documents that I am a PhD students in Canada. I would assume it is fine and they accepted my excuses and believe I left on time.
How can I make sure I will not get any trouble next time I re-enter because of this issue? Should I expect much trouble?
My passport is swiss and I live in Vancouver, Canada with a study permit.