When a rabbit 'throws' itself into the sides of it's cage, it is usually because the rabbit is panicking and terrified. It's possible something frightened your rabbit, especially accompanied with the thumping. Or something else may have happened, like a health condition that caused your rabbit to panic.
If your rabbit is truly sneezing and doing it consistently, there may be some sort of respiratory issue going on. They won't always get a runny nose with it. The event of your rabbit panicking could also be related if she might have choked and this has lead to the current possible respiratory issue.
If by 'throwing' herself at the sides of the cage, you mean she wasn't actually running into them but biting or going at them because she wanted out, then this could just be a boredom and behavioral issue. And if it isn't sneezing that she is doing but more like grunting at you because she is upset at something, It could be that she is upset about you being gone and is letting you know it.
From your description it could be a possible health issue or it could be behavioral. You will need to determine which is actually going on. If you aren't sure you could video it and post it. That may help us figure out what is occurring. If she is in fact sneezing and it is happening frequently, then it would be a good idea to have her seen by a vet. This is especially important if she is showing signs of bloating and a distended belly. If you really do feel like her belly is distended and not normal, you really should have her seen right away despite her not showing any signs of lack of appetite. A bloated belly can very often indicate a serious health problem. If you take her to the vet, it would be good to bring a fresh fecal sample for them to test. Is she eating her normal amounts of food? Any changes in her poop, is it mushy or smaller than usual?