We've had some excellent vegan options on transcontinental flights. A tip for future travelers: Try to remember to request them at least a week in advance.
As for the work issue, it's probably quite easy to ask in advance for dietary restrictions to be addressed when it's a function at your home office, but when you travel to offices in cities you've never visited or internationally its more complicated - you don't the ropes: who's ordering the meals, whether they are being catered by a local company or by a chain, or if they give you a meal break where you can go and get something yourself. Believe me, it can be a challenge, despite one's best intentions.