Plugged tire

So while mowing my pasture this past week I must have ran over a goathead weed. Because I noticed the next day my front tire was flat. Took it to my local Les Schuab tire store to get it patched. Well they put a plug in it instead. Is it safe ? Never had a plugged tire before .
On a side note are the Carlisle A.C.T tires that came stock on my 650XT that weak ?They only have 65 miles on them .
Thanks Allen