US Wireless is not reporting with the SEC since late 2008, so their PRs don't get the backbone of an 8-k filling. The merger is just a speculation at this point altogether. It is strange that they announced it without completing due diligence first, and at the time when the market is already excited.
Previous announcements of merger candidates had little effect on the stock price, even with one of the mergers later going through.
The last time this stock got a similar price move was in February this year. A short lived rally later pointed to nearly 90% price decline over one quarter.