Those little white balls don't hit themselves into the holes!
More seriously, the arrangement with Lendl is that he's only expected to turn up to slams, plus one of their warm-up tournaments, as well as some of the training. He may have been in Miami, just not there every day. We didn't see many photos from there, so it's impossible to judge. Arguably, most of the time in Miami was for a bit of acclimatisation to heat and humidity, and adjusting to hard-courts. As he lives in the general area, I'd be surprised if he didn't turn up at some point - assuming he was back in Florida. I recall some talk of a debrief from Wimbledon happening.