MThank you all for your help. I had contacted the hotel hoping they could recommend a car service. That worked well in Rome hotels. This hotel directed me to the nearest taxi stand. At 3:30 AM! Not when last time at Barcelona hotel I was going to wait outside for taxi. The clerk warned against it, "You will get robbed."
A helpful friend from my roll call recommended a service.
Following Flyer Talker's advice I sent email inquiry to Lufthansa re:check in counter opening time. They said they will reply. Giving it few more hours then will call.
I also was relieved to learn that BCN is open 24/7.
Thanks again! (forgive that initial M....when I try to correct on this site with the iPad....all gets erased)