Posner - Mootness & Vacatur.
A party waives the right to vacatur of a lower court's denial of a preliminary injunction by not requesting it upon appeal in a case that has become moot. Circuit practice is not to typically vacate lower court holding in this situation. Although the decision below was adverse to petitioner, it was not preclusive as to the issuance of a permanent injunction.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2015/D12-23/C:15-1881:J:Posner:aut:T:fnOp:N:1676912:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.