I am not sure there is a good trick for the tshirt (and what there is might vary between cotton, polyester, linen and the like). Try the usual wash or maybe a stain remover. I have stained plenty of my stuff but it is usually a work apron or shirt for a reason.
On the wood front then trouble is that is a wood ageing/staining trick -- you often stick steel wool in vinegar, leave it for a while and then use that to make oak appear nice and aged. Some woods to far less with this (pine for one does pretty little compared to cedar or oak) so you might have that to your advantage. Also is this wood planks, wood board, laminate (will often have a plastic layer on top and also reduces options for other things) or something else?
Depending upon how long it sat around (if you dried it quickly then it might not have had time to sink in deep) and the concentration to begin with (steel wool in the scenario above tends to be picked for a large surface area, if it has to go through rust first and was only screws underneath it then you might well be lower). It might also change over the coming days -- when you first do the wool trick it looks awful, wait a while and it will look far nicer.
If I am doing fine furniture and accidentally hit a nail into the wood (say one rolls under something I am assembling on top of it) which in turn does the whole tannins thing and makes a nice stain I might remove the divot (put a clothes iron on a damp rag and let the water swell it and bring it out) but call it character. If I am refinishing old wood (pains me a lot of the time to do but if the client wants it...) then I tend to favour mechanical removal methods here -- that is to say plane or sandpaper, scraper might not be enough but try it if you want. If it is a laminate floor then mechanical is not really an option, at least for some and refinishing will likely be on the cards either way.
I don't really have any chemical means, certainly not any kitchen chemistry methods, lasers might do something but you probably don't have that as an option.
The crazy man's method would be to see about staining the whole floor, or maybe removing the section where it happened and putting it somewhere inconspicuous. Depending upon the ways something was built then the attic/basement/outside shed might also contain a few old planks or laminate sections that might be able to replace the whole thing.