Very likely it dried out while you were out of town.

Another possibility is that you overwatered it by putting extra water in pot knowing you are leaving for the extended weekend.
I'm myself killed bonzai azalea this way just in 5 days.

If I understand that you typically keep this plant inside next to your window, but left it outside while you were gone....that's what happened to it. Add whatever the water situation was on top of that.

Your azalea (the next one) should be kept outside at all times, in an area protected from the full sun. Mine, which are probably more mature than yours, get watered every day except in the winter or if the weather is very dark and rainy (which hasn't happened this summer/fall). I do bring it them in to an unheated but protected location in the event of a severe freeze (20o).

This azalea might not be a goner yet, only time will tell that for certain. But I would certainly give it a fighting chance by keeping it outside where its chances of coming back in the spring are much greater. Azaleas are rather difficult to grow inside...they don't the location much, lol.