I got a pretty spectacular draw fail just now...
Elanchana Destler draws Laboratory, Laboratory, Throne Room, Gold
Elanchana Destler shuffles deck
Elanchana Destler draws Gold
Oh good, two labs! This will be a good turn to double province!
Elanchana Destler plays Laboratory
Elanchana Destler draws Moneylender, Estate
Elanchana Destler plays Throne Room
Elanchana Destler plays Laboratory
Elanchana Destler draws Province, Estate
Elanchana Destler plays Laboratory
Elanchana Destler draws Duchy, Duchy
...or not.
As an aside, it is usually better to throne the first Laboratory here, to maximize the number of cards you can draw, and thus your chances of kicking off whatever engine you've got going. The disaster scenario, the way you played it, is that the first Lab draws a Throne Room, and then when you throne the second you don't draw anything useful. If you had throned the first one, you could now throne the second.
If you are starved for +actions instead of +cards, then the way you did it could be better, hoping to Throne-Throne-Lab-Lab, which saves you an action compared to my way. But if you have plenty of actions (as you often will if throned Labs are your backbone), then there's no need to be greedy and hope you can throne a throne: the potential upside is only one extra +action, and the downside is your turn ends way too soon if you draw badly.
Since your deck
at that point contained only two terminals in total, you definitely didn't need the actions! Obviously it wouldn't have mattered, since you didn't draw your other Throne Room, but it's best to avoid the possibility of danger when you can.