If the plant is shocked by either cold or severe cutting back, it will probably not bloom very much, even in a greenhouse. It takes a lot of time and momentum for good floral stems to develop. The bast bet is to dig it up and carefully prune it back, leaving stems that have buds that are about to bloom. You can tell if buds are going to emerge by looking at the tip and noticing that there are many more small pairs of leaves, and by pinching the bud lightly to feel the beginning of the bud by the relative thickness to ordinary tips.

Try to move the plant to an environment that is not radically different from the outdoor conditions, or there will be a lot of leaf drop.

Don't over water and over fertilize.

Every year I would buy a pineapple sage plant from garden center.
3 years in a row it never survived the winter. In spring 2009 I bought
another one (only $4), but this time planted it very close to my brick
house. Too my surprise it came back up this year. We had snow last
winter too. It bloomed beautifully this fall. Hopefully it will survive
again this winter.

One thing about pineapple sage, it is not easy to collect the seed. You
have to look for the little dried up flowers. I think I collected maybe
9 seeds.