Ricky, your tenses are not quite right. I will explain the forms and names of the tenses here.
Each verb has a base form, a he/she/it present form, a past form, a past participle form, and a present participle form, and some verbs a few more. Below are the forms of one regular and two irregular verbs:
Base form: notice - see - have
He/she/it present form: notices - sees - has
Past form: noticed - saw - had
Past participle: noticed - seen - had
Present participle: noticing - seeing - having
Both the past form and the past participle form (of regular verbs) are made by adding “(e)d” to the base form, so that they look the same - but not for irregular verbs, as you can see.
Each form is used in several tenses. Here are a few of the active tenses (there are also passive tenses):
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Present simple: base form or he/she/it present form: I notice/see/have, he notices/sees/has
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Infinitive: base form: (to) notice/see/have
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Present continuous: base form or he/she/it present form + present participle: I am noticing/seeing/having
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Past simple: past form: I noticed/saw/had
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Past subjunctive: past form: I noticed/saw/had (only the verb “to be” is different)
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Present perfect: present simple of “to have” + past participle: I have noticed / I have seen / I have had
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Past perfect: past simple of “to have” + part participle: I had noticed / I had seen / I had had
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Past perfect subjunctive: past simple of “to have” + part participle: I had noticed / I had seen / I had had
As you can see, the past subjunctive and the past simple look the same. The past subjunctive is rare, except in if-clauses. A past form in an if-clause is usually a past subjunctive. “In case” is nearly the same as “if”, so we have an if-clause in your example. All this also applies to the past perfect subjunctive. So we could have a past perfect subjunctive in your sentence. But this “hadn’t noticed” there seems to be wrong, so we’d better not spend time on that. If you want to know more about the subjunctive, I am sure you can find a page about it through Google.
“Did” is the past form of “to do”, so “I did not notice” can be either past simple or past subjunctive. “To do” usually goes with an infinitive, and an infinitive doesn’t change anything about the tense of the main verb, so “did not notice” is still past simple or past subjunctive: it is simply the negated past simple, that is the past simple with “not” added. The reason why “did” is added is that we cannot say “*I not noticed”: in modern English, we need to add a form of “to do” in negations or questions. That is except when there is an auxiliary or modal verb present: in the past perfect, the past simple of “to have” is an auxiliary verb; this means that you can simply say “I had not noticed” to negate the past perfect.
This was all about forms and names. If you want to know more about how to use the tenses, I’d need to write tens of pages; so perhaps you’d better browse this site for pages on the various tenses, or Google them.