You should be able to find your vote-code in the results, and can see whether it got added correctly. You may also investigate all other votes, read their comments, and generate vote-counts from the data yourself, to verify the presented-vote-count is accurate. And to check which votes the vote-administration "herded", to see if this is agreeable.
With every vote comes a unique "password", which looks exactly like a vote-code. In some ways, it is a reserve vote-code, which remains a secret between you and the vote administration. It can be used to identify you as a valid complainer, to correct your attacked vote. Obviously, the complaint itself could be the attack, therefore registering a complaint shouldn't be taken lightly, additional proof of identity may be required. This is in the hands of the vote administration.
In case a vote was significantly attacked/manipulated, significant numbers of voters should find out by checking the results. This may produce a cascade of more checking by more voters. If the problem persists, ...