Well the company owner stopped by today and picked up the envelop with the two pieces. I asked them to keep the envelop and pieces securely as evidence in case anyone wanted to look at it eventually.

They said later that they think this material came from their supplier of ground beef tenderloin and is called silverskin, so it wouldn't be plastic but some inedible piece of the cow.

After some back and forth they understood that having 1/2 inch pieces of material that resembles plastic in their ground beef is abnormal for Canada and needs to be reported once the source is determined.
He is waiting for their chefs to come in during the week and will get back to me.

It's a big relief to find out it probably wasn't plastic I ate. I ordered from a different meal service company and am awaiting delivery today. Ordered Indian food yesterday and have got lots of left overs if for some reason they don't show up.