Because we made a deal with Parma for a season long loan. So if we desperately want him back, we need to make a new deal with them, which will cost us.
Apparently, at first we thought Lanza was a necessity for us, but some people have changed their minds. One can only assume that this change of heart happened because the cost was too high right now when compared to what Lanza would add to our team these 5 months.