Need honest opinions/answers

If you dated someone for a long time (little more than a year relationship) in which you had strong feelings for this person but ended up doing something very hurtful (Cheating, using, lying) to them towards the end of the relationship without much of an explanation on your part and somewhat just disappered. Never said sorry or gave them their stuff back. Than you decided you wanted to talk to them again months later ... maybe to see how they are doing or to give their stuff back or to say sorry but found out they changed their number and obviously never told you about it... They never cussed you out or did anything to "get you back" they just dropped it and changed their contact info. How would you feel about that? Would you find other ways to get in contact with them or just let it go because you can see that they were hurt by you and didnt want you to be apart of their life anymore. Would it make you feel worse because you never got a chance to say sorry or say what happened or would you have an "oh well" kind of attitude.

What if out of the blue they hit you up from their new number... how would you handle that? Would you be nice and receptive or have some sort of a confused attitude with them?

Would really appreciate all the responses I can get and diferent views from different people. Thank you.