I think it's a known problem - and a very annoying one. I use a D300, and I've learned not to switch the camera off once LR connects. Then I forget, and have to keep everyone waiting for a couple of minutes until LR manages to find the camera again.
By the by, I believe on the D300 that the power consumption with the camera on but inactive is very low - little more than with the camera off. Once the meter, display, lens stabilisation, LCD backlight etc have all timed out and switched off (after a few seconds, depending on your setings), there's little power used. As the D700 is almost identical to the D300 (just the larger sensor and related differences) I would expect the same to be true of the D700.
