If you were gone for a little less than three months, rather than three months or more, it qualifies as a "short gap" in coverage and so you're exempt from the requirement to have insurance. From the IRS website:
- What are the statutory exemptions from the requirement to obtain minimum essential coverage?
- Short coverage gap. You went without coverage for less than three consecutive months during the year. For more information, see question 22.
Otherwise, I suspect that you're out of luck. There's an exemption from having coverage if you're gone for an entire year; from the U.S. State Department's website:
U.S. citizens living abroad are generally subject to the same individual shared responsibility provision as U.S. citizens living in the United States. Starting in 2014, the individual shared responsibility provision calls for each individual to have minimum essential coverage (MEC) for each month, qualify for an exemption, or make a payment when filing his or her federal income tax return. However, U.S. citizens or residents living abroad for at least 330 days within a 12 month period are treated as having MEC during those 12 months and thus will not owe a shared responsibility payment for any of those 12 months. Also, U.S. citizens who qualify as a bona fide resident of a foreign country for an entire taxable year are treated as having MEC for that year.
It may still be cheaper to pay the tax penalty for the three months in question than it would be to buy insurance that's valid in the US, though. You might want to look in to how much the penalty would actually be for you. The penalty for full-year non-coverage is $325 or 2% of your 2015 income, whichever is higher; this would be pro-rated for the parts of the year in which you don't have coverage, so your penalty would be about a quarter of this amount.
Disclaimer: I am not a lawyer or a tax professional of any kind, so my reading could be entirely off-base. There may be other exemptions that I'm not aware of.