Car FOB malfunctioning again?

A few weeks ago I asked a question about my car FOB not working. Once in a while it would not unlock the car with the FOB and when I used the key, it wouldn't let the car turn on and the car would start beeping very loudly. A few days after I asked the question on here, the battery died. Thinking it was an electrical issue draining something somewhere, I took it to the dealer since my car is still under warranty. It's a 2008 Hyundai Accent. They told me all it needed was a new battery, so I bought one and everything worked perfectly. The FOB worked, the car turned on, etc. About two days ago, the FOB issue started up again. I immediately stopped using the FOB so that it wouldn't set the alarm. I took the car back to the dealership and they tested the FOB several times and it worked. I told them that sometimes it doesn't work and I can't start my car and I don't want to be stranded. They have pretty much told me that unless it's currently not working while it's in their possession, they can't do anything to help me. I don't want to take my car home and then be stranded somewhere in the middle of the city! My car is under warranty so I am not sure if I can take it to a random electrical mechanic. What do I do? I can't believe they're just basically telling me "sorry about your luck"!