I'm going to venture a few hypotheses, since we can't 'know' off the bat.
- The tea was hotter than usual on your tongue: the evidence for this is that sensation on your tongue was reduced even after drinking the tea. Possible physical reasons:
- You removed an important safety device: the temperature sensors in your lips. When you sip, your lips will tell you very quickly that the cup and/or tea is too hot. Without that, you could easily drink it too soon and not realise it is too hot.
- You did not slurp: slurping is an effective method of reducing the average temperature of the liquid by bubbling air through it. It also draws from the top layer of the tea.
- You drank from the bottom of the cup instead of the top: Thinking about it, this is my top candidate; the top surface of the tea will be much cooler than the bottom, and the straw almost certainly was near the bottom of the cup.
- You got more tea by drinking it through a straw: A larger volume of tea would stay hot for longer in your mouth, so instead of immediately cooling when it met your saliva, it could instead heat your saliva and remain hot on contact with your tongue. Possible mechanism:
- If you draw liquid up a straw, there will be some overrun when you stop sucking. So it is difficult to drink just a little, as you have to wait for it to arrive before you know to stop sucking. This way, you could easily draw in much more tea than you would by sipping.
In sum, I would hypothesise that some or all of the above occurred, particularly that you drank hotter tea from the bottom of the cup. Putting them together, though, is a recipe for disaster; you accidentally draw in more tea, the tea is hotter, it remains un-cooled by any slurping and you have much less warning from your lips that it is so hot. Result is burnt tongue.
By contrast, you want the coldest, most carbonated part of a cold drink to quench your thirst, so a larger quantity of the drink from the bottom of the cup with no chance to warm up is better, rather than worse.