I'm not an expert but maybe the icing was not stiff enough? Or maybe in the bowl it was stiff enough, but due to heat or maybe you have "warm" hands and the heat from your hands was causing it to melt". As you found out, when it "melts" you lose control over it. Maybe need to make several smaller filled icing bags and keep some in the refrigerator and alternate them, switching out when you notice a change in the texture of the icing. HTH's.
Pam 
I see you're from Houston. I live in high humidity and heat, also. I have had the same issues. If it's melting now and not even July, you'll probably continue to have issues. I don't know what recipe you are using, but you'll need to experiment and change it up. I use a butter/shortening mix. I found decreasing the liquids solved the issue. I make the decision how much to use as I'm making my buttercream. Just depends on the day. I find no matter how long you put the piping bag in the fridge, in the end, it will melt if you haven't made some type of adjustments. Start playing with your recipe and you'll soon be getting good results.
Use Indydebi's buttercream recipe which is posted in the recipe section. Not inly does it taste great but it will hold up in hot temps. Your borders will not melt and roses will not wilt. I tested a dummy cake decorated with lots of boarders and roses on the side of the cake by putting it directly in the sun at 108 degrees and the cake was still perfect after 8 hours
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