If at all there was any legal action that was taken on you, by now you could got an information about it.
Since you are basically a British citizen, and there are no details about your passport available with the local police there is no possibility for the local police in Goa to implicate you in the case as you apprehend now.
Besides, the LOC is valid only for a year after the date of its issuance.
Since this is not a very major case or heinous crime (because it would have been a case for possessing drugs in small quantity), there can be no LOC or red corner notice.
In my opinion since it is clear that you were advised by an advocate to leave the country then, it is clear that there was no case filed against you, besides it is more than a decade, by now any case pending against the other person also would have been disposed.
Therefore instead of enquiring about the possibilities of LOC or any other pending case against you, it would be better that you undertake your proposed travel to China without fear. There are no possibilities for your passport details to be available in any country's immigration counter.
The LOC will be valid for a period of one year from the date of issue and name of the subject shall be automatically removed from the LOC thereafter unless the concerned agency requests for its renewal within a period of one year.
More information on LOC:
With effect from 1.1.2011, all LOCs with more than one year validity shall be deemed to have lapsed unless the agencies concerned specifically request for continuation of the names in the LOC. However, this provision for automatic deletion after one year shall not be applicable in following cases:
ban-entry LOCs issued for watching arrival of wanted persons which have a specific duration);
loss of passport LOCs ( which ordinarily continue till the validity of the document);
LOCs regarding impounding of passports;
LOCs issued at behest of Courts and Interpol;
In exceptional cases, LOCs can be issued without complete parameters and /or case details against CI suspects, terrorists, anti-national elements, etc. In larger national interest.
In my opinion you do not fall under the above category, hence you can remain fearless. '