@Newtohere I agree that the plan seems to have gone. They're not hiding it on you - the public page at https://www.publicmobile.ca/en/on/plans#ALL (for Ontario - if you need a different province, you can switch at the top of the page) shows all plans, and is not behind a login).
However, Black Friday is coming up fast, and there's definitely a chance that the plan returns or a better plan is offered. I assume that your "next month" is December, and if if is, it may make sense to wait and see what shows up in a few weeks.
If there's no better plan, you'd have to use the $30 US add-on (which gets you 3GB of data plus calling/texting in the US for 15 days). That's definitely more expensive than what you were doing but it's a supported approach and won't leave you risking not returning to your plan. Also, you could switch to paying for your $39/20GB plan for 90 days at a time, making it $34 a month (a current deal). That would save you $5 a month (so $60 a year, paying for two US trips all by itself, and costing you less than what you were doing) and give you 60 GB of data for us over 90 days.
