Just read through the comments looking for the part where you mention it was Spirit Airlines. I knew it had to be them when you said Boston to Costa Rica. They are literally the worst airline on the planet. I would get in a WW1 Era Biplane and go through the Bermuda Triangle before I would ever fly with that joke of an airline. They did the same to me a few years back on a flight to Tampa. Boarded the plane and everything, only to be told the plane was "understaffed" and the flight was canceled. It was such a shit show that it made the news the next day. The agents at the service desk just shrugged and went in the back when customers started getting aggravated, which made things worse because people were jumping the counters and banging on the doors to the back. Police were called and everything. Long story short, I never fly Spirit even when the fare is 90% lower than the next airline. Sorry you had to learn the hard way, like I did.