Margarita Mint Failed to Survive Winter

Last year I purchasted a 'Margarita Mint' plant from Richters Herbs in Ontario, Canada. It grew very well last year, but was completely dead when I checked it this spring. As of now, it has not revived at all.
I've never had a problem growing any mint plant. Is there something special about this one?

Margarita mint has only been on the market for a few years so we do not have a lot of feedback on its hardiness. But based on our own experience growing it we have no indication that it is any less hardy than other mints such as spearmint, peppermint, etc. However, the winter of 2004-2005 was hard on many herbs, not because of extreme cold but because of usually late freezing and thawing that occurred throughout much of the northeastern North America and elsewhere. When a plant begins its revival in spring a late freeze with heavy snow and ice can be lethal. Even if you have other mints that survived the same conditions, a newly established mint – whatever the variety – is more susceptible to succumbing to sudden unexpected shocks in spring.
In fact, for the first time in decades we lost herbs in our fields this past winter. Herbs such as lavender that have always made it through our zone 5 winters did not come back this year. So it does not surprise us that your Margarita mint failed to come back. We view the past winter as exceptional and we are replanting our herbs with the hope that another winter like the last will not occur again for many years.