Your parent's could have claimed you if you graduated in May, 2016.  The requirement is if you were under 24 years of age and a full-time student for at least 5 out of 12 calendar months in 2016, your parents can claim you as their dependent.  The month you graduated counts so there are your 5 months.  They may want to amend their tax return and include the 1098-T on their tax return so they will not only get you as their dependency exemption but will also get the education credit.  I have included a Link below just in case they want to amend their tax return:

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed