Looks like it, yes
Alonso managed quite a few laps after getting back on track too though, so it's likely that it was just a wheel bolt/nut defect on his Mclaren... hopefully for them, anyway.
Renault with 99 laps but relatively lower top speeds; makes sense after their announcement that they'll be focusing on reliability at the start of the season and will look to improve performance later on.
Oh well, it's only the first day of testing anyway, the priority for the teams is surely just gathering data at this point. Hopefully the weather conditions will improve for tomorrow, there were even talks of testing being extended to Friday.