Unfortunately for you, shoplifting is a minor offence, but it is still a criminal offence. Police does not have to be involved. If you were summoned to go to Court it means that charges were laid against your person.
Now, Failure to Attend (Appear) in Court when summoned to is a LOT MORE serious offence. It is actually a major federal and criminal offence. Most likely a bench warrant was issued against your person and you now have two offences in your criminal record, you are wanted by the Police and your chances of being admitted back to Canada (if it is not just to appear in Court and/or go to jail) are slim to NONE.
If you ever want to be able to come back to Canada, you would need to contact a criminal defense lawyer and one that is specialized in immigration and rehabilitation and try to get this issue resolved and obtain legal advice before you do anything else, especially trying to obtain a new visa, as this will otherwise most likely stick to you for the rest of your life.