The Luck Of The Irish

Oh yes, Liam was a lucky man last night...
Out for drinks and dancing with the girls at an Irish bar, I was hit on by Liam, a carousing, cartoonish character who must have woken up this morning with one hell of a hurting hangover!
Liam is not my type. I am not into old guys. I am not into drunk guys. I am not into having the same introductory conversation over and over again because someone is so loaded that they can't remember what you just said...
Once my late mates arrived, I was able to extricate myself from Liam's lecherous presence. He did a jig over to our table a couple of times, asking if he could buy us drinks. The answer? No, thanks! I knew that if we allowed him to buy a round, we wouldn't be able to get rid of him.
The mistake I made that evening? When he asked for my phone number, I blanked and, not knowing how to tactfully decline, I timidly divulged my digits. Why? Because I am a wimp. How do you politely deny giving someone your phone number? I've never been good at that. I feel badly for them. I'm too empathetic. However, it is pathetic to not be able to stand up for oneself and say the right thing. So, what is the right thing to say? Are we to lie ("Sorry, I have a boyfriend.", "Oh, I'm due back at the mental institution first thing tomorrow morning.." or "Unfortunately, I flushed my phone down the toilet earlier...")? Are we to give the wrong phone number (or, the right number to someone who has wronged us in the past?!)? Sounds like bad karma to me...
Lucky Liam sure found the pot of gold. I'll let you know how our drunken date goes. Cheers!