Please help out!
I took out my Oxalis plant outside for entire summer last year and once the pot got heavy and overgrown with those beauties, I decided to leave it outside over winter. I should have brought him back in, but I read into this plant and while many articles insist that it is primarily a houseplant, this one article was a bit misleading (apparently). It basically said that False Shamrock/Oxalis plant bulbs are very durable and can survive months and month of drought, shade, and other unfavorable conditions. So I figured, when conditions are back to ideal (hot NYC summer), the bulbs should come back to life. So far, there is no sign that Oxalis ever lived in that pot. I sifted through the pot to retrieve all bulbs and soaked them in a water for few days in hopes that it will bring them back to life and replanted back. Nothing. It is mid-July and I water that pot often, and no sign that anything will ever grow resembling oxalis. Did I kill my plant for good?

You should have considered winter cold also. If they aren't up by now, they are gone forever.

Hi & welcome! Was it the purple one, Oxalis triangularis? If so, it's hardy (able to survive winter) to Z6. If your zone is lower than that, it can't survive outside for winter.

Plants that can survive any degree of non-tropical winters are assigned a range of zones. You can see the range of zones for O. triangularis here:

The conventional wisdom is to subtract a zone for plants in pots, so if you are in zone 5, it would be reasonable to expect Z4 plants to be able to survive, but not necessarily plants only hardy down to Z5 (or a higher lowest zone.)

You can find your zone here:
http://garden.org/nga/zipzone/