Depending on the med, your insurance may not cover any additional supply for the next XX number of days. I'd probably call the doc first to see if he can write a similar-but-new script, or using an acceptable alternative med to get you by. Second would be the pharmacy if they have any suggestions or tricks. Last would be the insurance. Maybe they can temporarily waive the supply restriction for your account.
And yeah, as mentioned, in the future bring only as much medication as needed by your days on vacation, plus a small buffer....not your entire 90-day supply.