I'm going to steal back my own socks from my girlfriend at a time we both needed socks
Why steal your socks instead of buying new ones?
They are mine to begin with.
While it is understandable to want your own property back, it would not be good to leave your girlfriend without something she needs. It would be better to share or get some new ones together.
How is it her fault she can't find them? What am I supposed to do wear my wrecked old socks?
Would it not be easier to just buy multiple packs of new socks? Taking them when she needs them seems so petty, what if she thinks you are un reasonable and breaks up?