First of all, the question as to whether you have been detained or put in jail refers to something criminal-related. Your lawyer is right, immigration and criminal cases are separate.
Your application will NOT be denied simply because you have been in an immigration case, unless that includes a criminal conviction. Only cases where you were jailed as per a competent judge's order need to be disclosed. CIC does not care about your overstay status as it does not affect your MORAL CHARACTER. Only crimes of moral turpitude will prevent you from entering Canada. If I were you, I would have done the same thing. You were arrested and then released immediately is not considered arrested and/or detained under legal terms.
Your FBI record even if it shows arrested or deported alien, will NOT disqualify you from a Canada visa, neither it will disqualify you for another US visa if you qualify for it. As soon as a visa officer looks at your FBI record, and determines that it is immigration related, he/she will have a I DON'T CARE attitude.
Only cases where you have been jailed/detained subject to a criminal charge needs to be disclosed. Even under such circumstances, you will NOT be considered ineligible for a visa simply bcoz you were jailed. You have to provide a court verdict with your application. It is the judge's decision that matters, and also whether the crime you have committed is considered a crime in Canada or not. Anyway, since yours is an immigration related case, your lawyer is right.
Taking into custody by Police is a normal occurrence in many of our lives. What matters most is whether you have been ordered jailed by a competent court of law. And whether you have been convicted of a crime that prevents you from meeting the good moral character definition.
Your answer NO to the question is right.
You will get the visa >>> Your previous history in the US will NOT prevent you from getting a visa or affect your application in any way.
HUSSAIN