Decelerating in a curve will force your bike to the outside of the curve (it's that physics thing again). It may seem counter intuitive but accelerating actually makes the bike lean in more (turn tighter). In other words you should have stayed on the gas or given it a little gas and it would have actually made getting back into your lane easier.
I used to have a sticker on my RT windshield that said "If in doubt, dont" just to remind myself that the moments hesitation (actually doubt) you sometimes get before doing something is your brains way of warning you that you are close to the edge of your skill or comfort zone.
I think you have it backwards. To quote Larry Grodsky ("Stayin' Safe," p. 169) "When asked to predict the path that a motorcycle will assume when gassed mid-corner, fewer than half of all riders correctly predict that the bike will straighten and run wide." Think about it: when the road straightens out after a curve, you open the throttle a bit and the bike stands up, or "runs wide," which is exactly what you want. I think the throttle is a fine way to "tune" your way through a curve once you are leaned over: starting to run a little wide - reduce the throttle; cutting in too soon - increase the throttle. Works great if the bike is in its power band, and for me, often easier than using a little rear brake or changing the lean angle.
I think the previous poster did the RIGHT thing in slightly closing the throttle. What he probably did wrong was not counter-steering hard enough and maybe not looking where he wanted to go. The reason to not abruptly close the throttle or hammer the brakes when you are leaned over is that either will shift the weight forward which may cause your rear tire to slide out and low-side you.
The OP we are commenting on figured out for himself how he could (and should) have avoided the situation. But we all make mistakes. Best to REALLY understand (and safely practice) these physics so, if we have to, we do the right thing.