I don't know about in your area but here in West Virginia, all stores have been out of stock of eggnog since the start of December. Walmart, Kroger, Target, all out of stock all month.
The reason is not a mystery. I thought maybe it was an egg shortage. But no. Virtually all the eggnog in the the country is made by one conglomerate, United Dairy. The decision for how much to make for the season was made in early November. Normally, they count on a 5 percent increase in demand each year. But this year demand is running 60 percent above their estimate and because it's a huge corporation, they can't react in a matter of weeks.
If the eggnog was made locally, makers could react in a few days. This is one of the downsides to giant nationwide companies making everything. Maybe lawmakers will consider history and examine the 1930s again when they don't have their eggnog this year.