If it says it's already in your library .. icon, then chances are it was spam. Some spam tricks LW into thinking the file was already downloaded; shows that icon. Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

The reason for your search problems seems not totally uncommon. It's happened to me on & off. It usually lasts for a few days up to a week.

It might be due to ultrapeers you are connected to, but not necessarily that reason, that the ultrapeer(s) is not responding with sending search information off or returning it.