Even buying your air via a third party you should have your airline's booking code and ticket numbers. Keep checking the airline's website for your trip's status using your booking code. If/when the airline makes a change, i.e. cancel or change flights that would result in a signficant schedule change, you should be entitled to a refund.
https://www.transportation.gov/individuals/aviation-consumer-protection/refunds
When the airline is at fault:
Passengers are often entitled to a refund of the ticket price and
associated fees when the airline is at fault.
Cancelled Flight – A passenger is entitled to a refund if the airline
cancelled a flight, regardless of the reason, and the passenger
chooses not to be rebooked on a new flight on that airline. Schedule
Change/Significant Delay - A passenger is entitled to a refund if the
airline made a significant schedule change and/or significantly delays
a flight and the passenger chooses not to travel.
https://www.transportation.gov/briefing-room/us-department-transportation-issues-enforcement-notice-clarifying-air-carrier-refund
Friday, April 3, 2020
WASHINGTON – The U.S. Department of Transportation today issued an
Enforcement Notice clarifying, in the context of the 2019 Novel
Coronavirus (COVID-19) public health emergency, that U.S. and foreign
airlines remain obligated to provide a prompt refund to passengers for
flights to, within, or from the United States when the carrier cancels
the passenger’s scheduled flight or makes a significant schedule
change and the passenger chooses not to accept the alternative offered
by the carrier. The obligation of airlines to provide refunds,
including the ticket price and any optional fee charged for services a
passenger is unable to use, does not cease when the flight disruptions
are outside of the carrier’s control (e.g., a result of government
restrictions).