1099-G's come from state governments, not the federal government.
Each state sends it out on their own schedule. You could call your state tax people and ask them.
In my state, there is a grocery tax credit which can be a few hundred dollars. It is possible to get a small refund that is less than the grocery tax credit, and in those situations a 1099-G is not sent because the refund is not considered taxable (because it's essentially the grocery tax credit being refunded, not income tax paid). You may have a similar situation in your state.