My bet is mild weather woke them or allowed new eggs to hatch and sent them looking for warmer pastures. In the past my success with not having aphid problems all winter meant making sure we were into full winter weather for several weeks before planting, and starting with healthy grocery store herb plants. Those critters can't live in a deep freeze but the eggs winter over in soil or plant material and they can show up again in spring. Once they start reproducing again they look for a warmer spot when it starts to turn cooler again. So if they can survive in the soil or plants, they only need enough mild weather to bring them out, and that can be just a week from what I have read. They thrive at 65-80 degrees and overwinter as eggs, then give birth to live nymphs as long as the weather is appropriate. Your house is like a perennial spring for them. I personally have never been successful in permanently getting rid of them once they have infested plants inside, so I just throw them out and start again. Or wait until I can plant outside again. If I was pretty sure there would be no more mild weather for several months (not hard around here) I would scrub everything down including shelves, floor, etc., to make sure there were no more eggs or nyphs that might have attached to some dirt or a stray leaf, wait a week or more of cold weather incompatible with their life cycle, and then try again.
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