The 128 GB model of the Surface Pro is no longer listed as in stock on Microsoft's online store, and we've seen several tweets and comments on sites like Business Insider and Supersite For Windows that say retail locations like Best Buy and Staples are sold out. The cheaper, 64 GB Surface Pro is still listed as in stock on Microsoft's site.
But the question remains how many units were available to begin with. There are several threads on Reddit where users complain retail locations like Best Buy and Staples only had a few Surface Pros in stock or none at all. Same goes for comments on the official Surface blog. It appears many retail locations only had a handful of devices to sell on launch day and quickly sold out.