Using merge and renaming your t vector as tt (see the PS of Andrie) :
merge(tt,z,by="row.names",all.x=TRUE)[,-(5:8)]
Now if you would work with dataframes instead of matrices, this would even become a whole lot easier :
z <- as.data.frame(z)
tt <- as.data.frame(tt)
merge(tt,z["symbol"],by="row.names",all.x=TRUE)