Was this sexual harassment?

An incident that happened to me last evening - I was walking back home. Nothing unusual on the street. The same hustle-bustle of traffic, busy people going about their jobs, the usual apathy around... I passed a couple of ladies on my way - a young girl of about 15 and an older lady (perhaps her mother). I... show more An incident that happened to me last evening -

I was walking back home. Nothing unusual on the street. The same hustle-bustle of traffic, busy people going about their jobs, the usual apathy around...
I passed a couple of ladies on my way - a young girl of about 15 and an older lady (perhaps her mother).
I noticed that the young girl was wearing a black t-shirt with something written on it. It's my habit to collect witty quotes and read t-shirt lines. Being curious, I began reading it. It went something like 'Unexpected Emotions...' The rest of it was hidden as she had crossed her hand over her belly.
Still curious, I did the unexpected (and probably unacceptable). I walked up to them and asked, 'Excuse me, may I read the line on your t'shirt?' The girl was probably puzzled and stared blankly. The older lady got it and said, 'No', and I walked away. End of story.

I can't remember if I asked sorry after the incident that's why this question arose. Did I need to be apologetic? Before leaving, should I have said at least a casual, 'Sorry for bothering you'?

I know sexual harassment is used for more serious offences and this may not qualify. Yet I ask. Introspection is my second habit and I can change / correct myself only if I know. Was this even remotely offensive?

A few points to remember:
They were total strangers to me and vice versa.
I was dignified in looks and manners, so that couldn't have scared them.
No wrong intention was involved here.
Update: PS: Girls, how would you have reacted if this happened to you? If someone walked up to you and said, 'Excuse me, May I read the line on your t-shirt?'
Would appreciate the politeness and manners or suspect I was hitting on you?
Update 2: PPS: I ask this question not to justify my actions, but to understand the other's perspective.
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