has anyone ever heard of this happening chemical burn

[bcla]

And just a random FYI: never mix ammonia and bleach. It's another chemical compound that not only can cause a burn but forms a gas that could kill you.

That would release a mixture of chlorine gas and ammonia gas called chloramine. It's fine in small amounts (it's used in municipal water) but everything is really about concentration.

However, there are a lot of things that shouldn't be mixed with liquid chlorine bleach. Other cleaning products contain ammonia, and almost anything acidic (even something mildly so) will release chlorine gas when mixed with liquid chlorine bleach.