I can confirm that Meecast behavior changed with the last version. For me, after a while, the widget dissapears in the locked screen, but it is related to the refreshing rate.
I either have to go to the notification screen, and usually that is enough to trigger the refreshing, or just wait for a while and the weather widget reappears in the lockscreen by itself.
This bug may be related with the refreshing rate of the local station sending it's data to Foreca or Weather servers...