"To get caught up (in something)" means that you spend a lot more time doing something than you planned. This can be something positive, like when you read a book and it is just so good you can't put it down. Or it can be negative, for example when you're cleaning the house and forget about the time so you miss a meeting. You always "get caught up" in an activity (reading a book, cleaning the house) and it often causes delay in your other plans. Hope that helps you :)

I got involved in something (else). Almost like to get 'ensnared' or 'trapped' in some activity. See: http://www.oxforddictionaries.com/us/definition/american_english/be/get-caught-up-in The person got involved in something and became too busy to pay attention to you, or get back to you. The sentence you give is not the most natural sounding. But if the person was giving you an excuse, this is the most likely meaning. The other possibility is to "get *caught up*". This means to succeed in doing work one should have done earlier. See 1.1 in http://www.oxforddictionaries.com/us/definition/english/catch-up?q=catch+up But this makes less sense here.