Does anything bad happen if someone uses an asthma inhaler for a cold, but didn't have asthma symptoms then?

Were you coughing? A rescue inhaler, no. If taken appropriately and it gave you relief within 5-10 minutes, this means you probably had some bronchitis.If it didn't have any effect and you stopped taking it, it didn't damage your lungs or heart. Now, don't keep taking other peoples medication. Especially, not maintenance inhalers. See your doctor and to determine if you need some prescribed for you.
Yes. Asthma inhalers are for specific types of symptoms. Using them unnecessarily may cause increased side effects. Always use your medication the way it was prescribed.