I have corel painter 2015 and I'm just in the very basics of learning this software... i accidentally deleted the wrong layer and i don't know how to get it back.. can anyone help? Is it retrievable?
undo by clicking CTRL+Z
If Gan's suggestion doesn't work, as a last resort you can try File > Revert which will take you back to the state your file was at when you last saved. You will have to consider whether this is worth it though as it may cause you to lose more than whatever was on the layer.
*Important* Be aware that I think this can't be undone therefore only do this if you saved after working on the layer in question. All work after the save will be lost.