Bar-headed geese have been observed flying over the Himalayas, even over Everest, so it is at least theoretically possible to have a birdstrike at 30,000 ft. I've seen this information in several reputable journals, so tend to believe it.
Also found this report, but haven't attempted to verify:
"The altitude record is held by a Rüppell's griffon Gyps rueppelli, a vulture with a 10-foot wingspan. On November 29, 1975 one was sucked into a jet engine 37,900 feet above the Ivory Coast in West Africa"
This might be the Lufthansa incident BlueEagle is thinking of.